Argentina have now beaten Ireland in three of the four World Cup meetings between the sides, but this 23-point winning margin was the Pumas' biggest against Ireland in Test rugby.
The Pumas were impressive, attacking with verve, and clinical when the tryline loomed. They will, you assume, be oozing confidence in the semi-finals, whoever their opponents will be, be it Australia or Scotland.
Talking of which. The last semi-final of this tournament will start in under 30 minutes and live coverage of the Twickenham encounter has already started which means it's time to shut down this live commentary.
To join my colleague Mike Henson, who will guide you through the match, simply click here. Bye for now.
BBCCopyright: BBC
'It's an Australia-New Zealand final'
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"I think the two form teams are Australia and New Zealand. I think they will contest the final. The winner will be whoever takes their opportunities."
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'We tried too hard and got loose'
Ireland 20-43 Argentina
Ireland coach Joe Schmidt: "The result just reflected the tour de force demonstrated by the southern hemisphere teams this weekend. We didn't get the start we wanted, but I'm incredibly proud of how we got back into the contest. When you try a bit too hard, you get loose, and they have tremendous speed merchants to take advantage. It was always going to be disappointing if we lost, but it was exacerbated in those final 15 minutes."
Felicidades Pumas!!!!
Barcelona and Argentina midfielder Javier Mascherano is also enjoying the moment.
'This is just the start for Argentina'
Ireland 20-43 Argentina
Matt Dawson
2003 World Cup winner on BBC Radio 5 live
“The consistency of performance is always key to success, and I also believe Argentina have some real game-breakers - players such as Tuculet, Imhoff, Cordero. They have probably learned from playing in Europe and playing in the Rugby Championship. There’s talk of them getting a Super 15 franchise too, so this is just the beginning for Argentina."
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The Hand of God calling
Ireland 20-43 Argentina
Leicester Tigers forward Jordan Crane tells Argentine football great Diego Maradona to book those flights to London.
The World Cup-winning football captain did, after all, say he would come over to support the Pumas again should they reach the semi-finals. Well, Diego, your boys did it.
Los Pumas!
Ireland 20-43 Argentina
Manchester City's Pablo Zabaleta gets all patriotic on us...
'Defence the difference'
Ireland 20-43 Argentina
Argentina wing Juan Imhoff, speaking to ITV Sport: “We will enjoy this moment but we know we have a tough game next week. Ireland played with a great intensity. We are a really good team in offence. But today we had a defence to make the difference.”
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Pumas still celebrating
Ireland 20-43 Argentina
Argentina's players are, understandably, still celebrating on the Millennium Stadium turf. Their fans have also stayed behind to soak it all up.
Juan Martin Fernandez Lobbe is accompanied by his children (I think) and is posing for a picture with his two toddlers with the scoreboard in the background. A never to be forgotten moment.
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Clarke 'gutted'
Ireland 20-43 Argentina
Former Open golf champion Darren Clarke is magnanimous in defeat.
Sanchez the leading man
Ireland 20-43 Argentina
Argentina outside-half Nicolas Sanchez was named man of the match for brilliantly orchestrating his backline and collecting 23 points. He is also now the leading scorer at this World Cup.
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'Argentina took their chances'
Ireland 20-43 Argentina
Ireland captain Jamie Heaslip to ITV Sport: "It's very disappointing to lose in such a big game. We didn't help ourselves at the start. We came back into it but we gave ourselves too much to do. This is a special group of players and a special group of fans.
"Argentina played a very expansive game. They stretched us. They took their chances. We got back to within three points - but then they took their opportunities to kick on."
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'Ireland's defence found out'
Ireland 20-43 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"It'll be a strange type of inquest because those 'What if?' questions will be there. There will be questions about their defence. They hadn't really been asked any questions in the pool stages. The back-line defence was found out. Argentina, a team with an all-round game, asked questions they couldn't answer."
'Ireland's execution wanting'
Ireland 20-43 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Ireland's execution let them down but you could not question their heart. Their execution was found wanting, while Argentina were ruthless. The northern hemisphere teams are competitive, but the southern hemisphere teams have finished when they've had the chance. They've not panicked. They've backed their skill sets. You have to take your chances when they are there."
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'Done your country proud'
Golfer Rory McIlroy, a four-time major winner, has tweeted his thoughts about the match.
Argentina through to the semi-finals
Ireland 20-43 Argentina
So, the south gets the better of the north once again. For those wanting to know, the northern hemisphere has always had at least one representative in the semi-finals in each of the previous seven World Cups.
It was only France in 1999 - the only time no home nation made the last four - but every other staging has seen two northern hemisphere sides in the last four.
The north's hopes now rest with Scotland, who will take on Australia at 16:00 BST.
Ambitious, joyous, ruthless
Ireland 20-43 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"I wonder how many fans of European teams will still deny that northern hemisphere rugby is out of date? Argentina were playing a different brand of rugby to Ireland - ambitious, joyous, ruthless - and it was great to see it work.
"They have learned well from their southern hemisphere rivals after their short stint in the Rugby Championship, proving that you only improve by playing opponents better than you."
Full-time
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Argentina show their class
Ireland 20-43 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"That try from Joaquin Tuculet has to go down as one of the finishes of the World Cup and also demonstrates one of the key differences between north and south - the ability to finish clinically, under intense pressure."
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Full time: Ireland 20-43 Argentina
England's World Cup winning coach Sir Clive Woodward is impressed with the Pumas.
Full-time
Ireland 20-43 Argentina
There'll be no first World Cup semi-final for Ireland. Instead, it's Argentina who will play either Australia or Scotland. Ireland's players on their knees, distraught, but they were well beaten.
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Ireland 20-43 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"The better team won. You can't cough up 20 points in the opening 20 minutes of a World Cup quarter-final and expect to win. The fact they got back into contention will only frustrate them more. Ireland weren't precise enough, made some bad decisions and executed moves poorly."
Full-time
Ireland 20-43 Argentina
Ireland recycling. Rhys Ruddock gains some metres... Robbie Henshaw tries to sashay through Argentina's defence, but the Pumas are alert to his shuffling hips... Ireland, eventually, lose possession... and that's the end of the match.
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Ireland 20-43 Argentina
Ireland hoping for one last hurrah before they depart this tournament. They earn a penalty 10m from Argentina's line, Jamie Heaslip thunders forward...
Ireland 20-43 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Argentina have played the last part of the second half so well that Ireland are lost for ideas. Ireland had a good spell of pressure early in the second half, but they haven't really been back into the opposing 22 since then. Argentina have won all of the big moments today."
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Penalty - Sanchez
Ireland 20-43 Argentina
Keith Earls with a late shoulder-charge on Santiago Cordero, but he escapes with a warning, the centre smiles wryly. The result is a chance for Nicolas Sanchez to practice his kicking, not that he needs it, and he knocks it over with his usual aplomb.
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Ireland 20-40 Argentina
Wales centre Jamie Roberts is impressed.
Ireland 20-40 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Absolutely fantastic score. Ireland have looked vulnerable on the short side throughout the second half. Argentina have been probing, and they've found the way through with a superb try.
"You have to take your hat off to Argentina. They've taken a lot of punishment, absorbed it and come back. Ireland have made one or two critical errors, Argentina have seen their chance and taken it. And that is it, I'm afraid, for Ireland."
Converted try - Imhoff; Sanchez conv
Ireland 20-40 Argentina
Dear Argentina fans, you may celebrate, you are through to the semi-finals. Juan Martin Fernandez Lobbe punching holes, offloading to top-poacher Juan Imhoff and the winger has enough time for a swallow dive as he dives over.
Nicolas Sanchez, in front of the posts... two points.
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Ireland 20-33 Argentina
Just the 10 minutes remaining and Ireland need to conjure a magic trick of Houdini standards if they are to escape from here. They have a mountain to climb, and it feels as if they have only brought flip-flops with them for the task.
Ireland 20-33 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"It was outstanding stuff from Argentina. The finishing was lethal."
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Ireland 20-33 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This all stems from Ireland not being able to clear their lines. They messed around with possession, and they're paying the price. They should have been up the pitch."
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Converted try - Tuculet; Sanchez conv
Ireland 20-33 Argentina
Argentina are celebrating. Joaquin Tuculet thinks he's scored near the touchline. Has he?
It was fabulous build-up play from the Pumas, the forwards doing the damage before the backs were let free to dazzle and outwit Ireland by going wide.
Joaquin Tuculet steps inside Rob Kearney, and has the strength to touch down in the corner despite Irish bodies on his back.
And it's a stunning touchline conversion from Nicolas Sanchez from the touchline, inflicting the mortal blow.
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Anybody nervous?
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Ireland 20-26 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This is just the time when Argentina might think Ireland are trying to play too much rugby now."
Ireland 20-26 Argentina
Pablo Matera, taking his eye off the ball, loses possession and could this be Ireland's chance? They need to be quick. They need to be clinical. But Robbie Henshaw stutters, going for the razzle-dazzle mis-pass when a simple through-the-hands move would have sufficed. Irish momentum dies a death.
Wallaby wants to know the score
Australia are on the way to Twickenham, but back rower David Pocock wants to know the score. Well seeing as you asked David, it's Ireland 20-26 Argentina, but it's close... and tense.
Ireland 20-26 Argentina
Ireland have just under 15 minutes to save their tournament. But Ian Madigan, feeling the pressure perhaps, kicks straight into touch. Fans groan in unison. The outside-half faltering under the spotlight.
Turnovers now level-pegging
Like Argentina in the first half, Ireland are now winning turnover ball with flanker Jordi Murphy leading the defensive effort.
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Ireland 20-26 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"Another three points for Argentina. These little bits of indiscipline can be crucial."
Ireland 20-26 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Ireland paid for not clearing pressure. Conor Murray should have found touch and given Ireland a chance to restart. All of a sudden, Argentina have kicked another three points."
Penalty - Sanchez
Ireland 20-26 Argentina
Daylight now between Ireland and Argentina. Outside-half Nicolas Sanchez shooting as sharply as ever, adding three points to the scoreboard and, in the process, becoming the most ruthless collector of points in this tournament.
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Ireland 20-23 Argentina
Joaquin Tuculet runs back with interest towards Ireland after collecting a high ball. The Pumas camped in enemy territory - and Devin Toner wraps an arm around the neck of the ducking Nicolas Sanchez and the referee has seen that.
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Ireland 20-23 Argentina
The penalty count has shot up for Argentina... Ireland certainly on the up whichever way you look at it.
They've secured turnover ball, only Conor Murray messes up, sending his pass into touch instead of Keith Earls.
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Missed penalty - Madigan
Ireland 20-23 Argentina
Ian Madigan trades power for accuracy, and his effort drifts wide. It would have been a mighty effort from near the half-way line had he succeeded. Twenty minutes remaining....
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Ireland 20-23 Argentina
Conor Murray sets his backline rolling, but Keith Earls is swallowed up as Matias Moroni smothers him in the tackle.
Argentina with put-in at the scrum... Irish fans serenading their team... The Pumas not the dominant force they were in the scrum, but Martin Landajo darts from the base, on to Santiago Cordero but the wing loses the ball in contact.
Marcos Ayerza, a bull-like charge through the ruck to take out scrum-half Conor Murray and referee Jerome Garces has little option but to give Ian Madigan the chance to level.
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Can Ireland nick it?
Ireland 20-23 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"Argentina guilty of playing too much now, their half-backs need to take this game by the scruff of the neck or Ireland will nick this.
"I honestly can't remember the last time I was so nervous at a rugby match. And I'm not Irish, and I'm definitely not Argentine."
Ireland 20-23 Argentina
Both teams have made a raft of changes, too many to mention in one go. One replacement, Facundo Isa thundering down the blindside - but Ireland aren't prepared to fold.
Magnificent by Rory Best, the Ireland hooker securing the turnover ball in the next phase. And the crowd are whooping and haw-hawing.
Penalty - Madigan
Ireland 20-23 Argentina
Ramiro Herrera is still on the field, but he should be apologising to his team-mates. His folly in this match has proved costly. Ian Madigan drags Ireland to within three points of the Pumas.
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Ireland 20-23 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Holy moly! We've seen it for the first time in the World Cup. Common sense has prevailed. There was no way that was a red card for Herrera."
Ireland 17-23 Argentina
Ramiro Herrera could be in trouble. The tight-head needs to smile sweetly here. He came charging in late into the ruck. Jerome Garces chats to his fellow officials, and he's let off with a penalty. "I give a penalty because you used your arm," says the referee. He could have seen red.
How's the heart, Brian?
Ireland 17-23 Argentina
Are you OK, BOD? The former Ireland centre appears to be struggling with the drama...
Ireland 17-23 Argentina
What an impact Luke Fitzgerald has made since coming on for Tommy Bowe.
He has run 57m, had two clean breaks, scored a try and set up Jordi Murphy's try with a wonderful run.
Argentina are missing tackles as a tidal wave of green comes at them, breaking the gain line.
Wingers Santiago Cordero and Juan Imhoff are the worst offenders having missed two tackles apiece.
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Ireland 17-23 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"That was a big swing there. Ireland had a fantastic attacking platform and took a couple of wrong decisions. They have to convert those chances. It was great defensive work by Argentina, though, and they've got down the pitch to get the three points and just calm things down."
Penalty - Sanchez
Ireland 17-23 Argentina
Argentina, though, in the line of fire turnover ball in the shadow of their posts... Juan Imhoff comes roaming from wide, the winger caught just before he could do some serious damage, but Ireland are penalised at the breakdown and Nicolas Sanchez stops the rot.
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Ireland 17-20 Argentina
It's all Ireland in these last few minutes. Ireland's fans are roaring. Rory Best finds his man in the line-out... the men in green roaming around Argentina's 22m... the centres punching holes in midfield... wave after wave of green crushing towards Argentina's defensive line.
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Ireland 17-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"What I liked about Ireland's last try was that they just gave the ball to Luke Fitzgerald a little earlier. Sometimes, they've tried to give the ball right on the advantage line, and they've found an opponent coming in at the same time. Instead, let them use their footwork to get over the advantage line. Fitzgerald got the ball early and bust the tackle to set up Murphy."
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Ireland 10-20 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"It is absolute bedlam in the Millennium Stadium, difficult to remember a noise like it. This could well carry Ireland to victory.
"Every Ireland charge, every Argentina mistake, every little thing that goes Ireland's way is greeted with ear-splitting roars. We have a grandstand finish on our hands..."
Ireland 17-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Luke Fitzgerald has brought Ireland back into this game with two fantastic breaks. Working that line-out, he stepped the defender and Jordi Murphy took it on for the try. What a game we have now."
Converted try - Murphy; Madigan conv
Ireland 17-20 Argentina
A honeyed platform for Ireland's backs from the line-out... Replacement Luke Fitzgerald the architect of the try, breaking loose from one tackle, evading the attention of Santiago Cordero and slipping the ball to the onrushing Jordi Murphy, who barges over the line.
Paul O'Connell, eyes like saucers, punches the air from the sidelines.
Ian Madigan adds the extras. Ireland have come out firing.
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Ireland 10-20 Argentina
Dan Tuohy
Ireland second row on BBC Radio Ulster
"Ireland have got to get the first score after half-time - even if it's only a penalty to make it a one-score game. Ireland must up the intensity now."
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Ireland 10-20 Argentina
Argentina start this half as they did the first, on the front foot, on Ireland's 22m. But Ireland are savvy at the breakdown. Flanker Chris Henry scavenging, stealing the ball with success and allowing Ian Madigan to ease the pressure with a touchfinder.
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Kick-off
Ireland 10-20 Argentina
Thirty players are on the pitch. There's one referee, too. They're battered and bruised, shirts muddy, but they're ready for another 40 minutes.
We're off. By the way, no team has fought back from a 10-point deficit to win a knockout game.
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The simple way of choosing sides as a neutral....
Keep the faith!
Ireland 10-20 Argentina
Ireland maybe 10 points behind at half-time but Irish fans must stay calm and, like comedian Johnny Vegas, keep the faith.
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'Pumas performance not a surprise'
Ireland 10-20 Argentina
Ireland 10-20 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"Ireland have found a way to get back into the game and are now competing at the breakdown. After their dreadful start, they will feel 10 points down is not an insurmountable deficit at half-time."
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Half-time
Ireland 10-20 Argentina
In terms of territory and possession it was even in the first half. Ireland enjoying 53% of possession and 56% of territory as they fought their way back from a 20-3 deficit.
Tackles? Ireland have made 64, while Argentina have made 56.
But it's in the metres made that we find a gaping difference between the sides (Ireland 185m, Argentina 308m).
Ireland 10-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Let's break this down: Who's the most disappointed changing room right now? Absolutely Argentina - despite their lead. Ireland weren't in the game for 20 minutes, but now they are. Argentina will be disappointed they haven't capitalised on being 20-3 up in a World Cup quarter-final. They threw the kitchen sink at Ireland, and could have had this game almost in the bag by half-time."
Ireland's fan power
Ireland 10-20 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"The Irish not out of this yet, this crowd could yet be a factor, it's ferocious when Ireland are attacking."
Ireland 10-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I get the sense that Ireland are coming back into it. But some of their decision making is a little bit off. They're taking complicated options when the simpler choice is better."
Half-time
Ireland fight back after Argentina's blistering start
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Half-time
Ireland 10-20 Argentina
Juan Imhoff, Argentina's prime poacher, with ball in hand on the left wing, but Ireland's defence are alert and the winger is ejected into touch.
Ireland secure on their own line-out ball and Conor Murray concludes a glorious half. Boot to ball, into touch.
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Ireland 10-20 Argentina
Ireland upping the ante at the breakdown as Argentina rumble around their 22m line. Cian Healy makes amends for his transgression at the scrum, slowing down play, and the Pumas are penalised for failing to stay on their feet. The pressure valve loosens a tad.
Ireland 10-20 Argentina
Super stuff from Matias Moroni, holding up a man in green in the tackle, gaining his team a scrum on the halfway line. Silly from Ireland, letting momentum slip.
From bad to worse. Ireland loose-head prop Cian Healy nose to the ground, and Jerome Garces has little option but to present Nicolas Sanchez with a chance to boot Argentina into Irish territory.
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Ireland 10-20 Argentina
Five minutes until the break and Ireland's forwards are rumbling, pushing Argentina's defence back inch by inch. But Argentina turnover ball this time just when the backs are set in motion. Winger Dave Kearney the man caught isolated on the floor.
Missed penalty - Madigan
Ireland 10-20 Argentina
Ireland's scrum is tree trunk still after wobbling in the opening minutes. Keith Earls running straight in midfield, but men in green get no joy so the referee halts play and penalises the Pumas for collapsing at the scrum.
Ian Madigan steps up, but his effort hits the uprights!
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Ireland 10-20 Argentina
Ireland have stemmed the blue tide and have pulled themselves back into the game.
Argentina are seeing less of the ball and their frustration is leading to penalties.
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Ireland 10-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"The main difference over the last 12 minutes or so is that Argentina haven't been able to get their hands on the ball and get some rhythm. They were using it well, so at least Ireland have stopped that."
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Ireland 10-20 Argentina
Ireland, pride pricked, are fighting their way back into the light, but they're now facing 15 men as Ramiro Herrera's sin bin is over.
Ian Madigan needs the attention of the medical staff. The Millennium Stadium turf turning into a scene of a Hollywood war epic.
But the outside-half is not going to leave this field because of a bone-crunching collision with Nicolas Sanchez. He's craving a leading role.
Converted try - Fitzgerald; Madigan con
Ireland 10-20 Argentina
Conor Murray collects Santiago Cordero's kick ahead, and Ireland punish the winger's loose kick. Robbie Henshaw finds replacement Luke Fitzgerald and the winger steps in from the touchline and, with an enchanting change of pace, touches down, presenting Ian Madigan with an easy conversion.
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Missed penalty - Sanchez
Ireland 3-20 Argentina
Argentina bossing the breakdown, and nearly every call is going their way. Nicolas Sanchez falters this time, though, but hang on... what's happening here...
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Ireland 3-20 Argentina
A rare mistake from a man in blue and white. Juan Martin Hernandez, the centre with usually regal hands, knocks on to gift Ireland a put-in at the scrum on the halfway line.
How will Ireland's forwards fare? Argentina are down to 14 men so the Irish scrum is firm but Robbie Henshaw loses possession just as the men in green prepare to spin it wide.
Ireland 3-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I'm worried about the options Ireland are taking. They're making too many wrong decisions. Sometimes, for instance, Conor Murray has gone right when the options are left. When you're making wrong decisions, it's usually a sign that your head's not right, and Ireland just aren't there."
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Pumas impressing
Current players loving Argentina
Ruthless!
Penalty - Sanchez
Ireland 3-20 Argentina
Ireland need to make the most of their man advantage, but they can't do anything without the ball. Argentina resolute in defence, dashing in attack.
Flanker Chris Henry is caught coming in at the side of the ruck and Nicolas Sanchez inflicts further damage in a dreamy start for the Pumas.
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Ireland 3-17 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This is a chance Ireland have to take. They have to capitalise on the fact that Argentina are a man down. If they can't capitalise, it will be such a boost for Argentina.
"Argentina want to run the clock down. That's what you do when you're a man down."
Penalty - Madigan
Ireland 3-17 Argentina
Ireland make the most of their opportunity. A neat touchfinder takes them to within 10m of Argentina's line and the Pumas crumble under the pressure, giving Ian Madigan a shot at goal in front of the posts. It's the sort of kick he could rattle off in his sleep.
Sin-bin - Herrera
Ireland 0-17 Argentina
Could that be the moment which swings the pendulum in Ireland's way. Ramiro Herrera with a late tackle on Keith Earls. The Irish fans in the crowd hiss when they see the replay. The prop is off. He can rest for 10 minutes
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Ireland 0-17 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I'm very worried. Ireland are really struggling at the breakdown. They're not making an impact in the rucks. Argentina are able to recycle the ball quickly, and Ireland can't get on the front foot."
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Ireland 0-17 Argentina
Argentina threatening whenever they have the ball. Number eight Leonardo Senatore thunders down the left wing, then Juan Martin Fernandez Lobbe makes hard yards in the middle of the field.
The Pumas in opposition territory at lighting speed. Nicolas Sanchez eyes up the drop-goal, but, oof, it's an ugly one. It hasn't the height nor the distance and it wobbles limply wide.
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'Worrying times for Ireland'
John Haughey
BBC Sport NI at the Millennium Stadium
"Stephen Ferris said during the week that he would be a bit worried if Argentina went six or 10 points ahead early on. Make that 17 Stevie, ouch."
Penalty - Sanchez
Ireland 0-17 Argentina
As Tommy Bowe was stretchered off, Ireland fans may have forgotten that their team was penalised leading up to that injury. Unfortunately for the Irish, Nicolas Sanchez is in ruthless mood, knocking a penalty over from 43m with aplomb.
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Ireland 0-17 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"The big difference between the two forward lines is Argentina are playing on the gain line and Ireland are playing in the transition zone. Ireland need to galvanise. They need to reassess their game plan and find a way to make sure they don't lose this game in the first half.
"Ireland have to retain the ball, get patient and get physical."
Ireland 0-14 Argentina
Tommy Bowe runs into Tomas Lavanini and the winger falls to the floor, face contorted in pain, as if he's run into the path of a tank at full speed, which I suppose he has.
The mobile stretcher comes on. It could be the end of the former Ospreys man's afternoon. Applause for Bowe as he leaves the pitch.
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Ireland 0-14 Argentina
It has been ALL Argentina so far.
The Pumas have run 145m with the ball, 123m more than Ireland.
Argentina have been trying to get the ball out wide and are playing an expansive game with right winger Santiago Cordero seeing plenty of action.
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Ireland 0-14 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Argentina are playing all the rugby. They're moving the ball around and Ireland are on the rack here."
Converted try - Imhoff; Sanchez conv
Ireland 0-14 Argentina
Argentina punching holes in midfield... Ireland's defence in disarray.
Santiago Cordero with a well-weighted crossfield kick from the wing and his fellow flyer Juan Imhoff reads the play beautifully, sprinting towards the posts and grabbing the ball and touching it down before it goes dead.
Fortune favours Nicolas Sanchez, the outside-half's conversion rattles the posts before falling the right side.
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Ireland 0-7 Argentina
An intense opening to this match. Argentina fired up and their forwards breathing fire, pushing Ireland back in the scrum. Ireland's set-piece crushed on their own put-in. Only the second time they've lost their own scrum in this tournament.
Ireland 0-7 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Great score from Argentina. They took Ireland through a couple of phases and found space on the outside. I was worried that Ireland's defence hadn't been tested so far in this tournament - and now we have the answer there. Ireland need to get on the scoreboard now, with a penalty, a drop-goal, anything. They look off the pace."
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Converted try - Moroni; Sanchez con
Ireland 0-7 Argentina
What a score! Joaquin Tuculet gathers the high ball, getting his men rolling forward. Brilliant from Santiago Cordero, who sucks in Rob Kearney and sets Matias Moroni free to gallop down the right wing.
Nicholas Sanchez as reliable as ever, adding two points from near the touchline.
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Ireland 0-0 Argentina
The Pumas keeping ball in hand before Nicolas Sanchez changes ploy, boot to ball, but Rob Kearney passes his first test. Ireland on the front foot, but Agustin Creevy brilliantly steals possession. Although, the Pumas fail to find touch from the resultant penalty.
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This could be close!
but not as close as Ian Madigan's new haircut
The Ireland fly-half, in for the injured Johnny Sexton, has marked the occasion with the shortest of short back and sides.
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Kick-off
Ireland 0-0 Argentina
Jerome Garces is the man in charge of keeping order for the next 80 minutes. He blows his whistle. Ian Madigan kicks it to Tomas Lavanini and it's safe to say this cracker has started.
Post update
Ben Dirs
BBC Sport at the Millennium Stadium
"The Irish have found full voice now, 'The Fields of Athenry' ringing out around the Millennium Stadium. But what's this? The Argentines quickly drown them out with some songs of their own. It's already epic in Cardiff, and we haven't even kicked off yet. Stand by for a classic."
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National anthems
Ireland v Argentina (13:00 BST)
Oh my, the salty tears are flowing from Argentina's players even before their national anthem kicks into full swing. It's as if someone's put a picture of their deceased childhood pets up on the big screen.
Next it's Ireland's turn to add their voice to proceedings and the men in green win the singing contest. Paul O'Connell singing along from the stands, standing with the aid of crutches.
Stirring stuff.
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Five minutes until kick-off
Ireland v Argentina (13:00 BST)
Cries of "ole!" rings around the Millennium Stadium, both sets of fans creating a crackling atmosphere.
The two teams in the bowels of the stadium, awaiting their call to march out from under the tunnel and into a wall of noise.
'Ireland win would be good for the game'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"It would be good for the tournament if Ireland made the semi-finals. If the last four are all southern hemisphere teams, that makes it more difficult.
"But it's not the end of the world for rugby union of there are no northern hemisphere teams in the semi-finals, though, because the best teams need to win. I think this has been the most competitive Rugby World Cup I've seen, and that's great for the game."
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'Think France 20 years ago'
Ireland v Argentina (13:00 BST)
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"One of my best rugby memories is in 2003, at the Adelaide Oval, when we beat Argentina to make it through the pool stages at their expense. One of my worst memories is 2007, when Argentina knocked us out.
"Argentina were just better than us that day. This team are slightly different. There's more to Argentina's game now. People ask: How do Argentina play? Think France 20 years ago. They've a big strong pack and a huge willingness to move the ball. They're a very well balanced side."
The king's speech
Ireland v Argentina (13:00 BST)
John Haughey
BBC Sport at the Millennium Stadium
"Paul O’Connell is not going to be on the pitch for Ireland but his former team-mate and BBC Sport NI columnist Stephen Ferris is expecting the big man to play a role in rallying the troops before today’s game.
"The Munster legend's speeches regularly bring tears to the eyes of team-mates so goodness knows what Paulie has planned for today’s occasion as Ireland aim to qualify for a first ever World Cup semi-final."
'Ireland should be massively confident'
Ireland v Argentina (13:00 BST)
Ireland lock Dan Tuohy on BBC Radio Ulster: “As was the case in the first two quarter-finals, physicality around the breakdown is probably going to decide the outcome today but I think Ireland should still be massively confident despite all their injuries and Sean O’Brien’s ban.”
Ireland looking for six in a row
Ireland v Argentina (13:00 BST)
Argentina's last win against Ireland was in the 2007 World Cup when they won 30-15 in the group stages.
But since then the Pumas' record against the Irish reads played five, lost five. Should the Irish take heart from that?
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SMS Message: Heart says an Ireland v Scotland semi, head says Ireland v Australia with an Oceanic final! Tom (suddenly in touch with his celtic heritage) in Kent
Heart says an Ireland v Scotland semi, head says Ireland v Australia with an Oceanic final! Tom (suddenly in touch with his celtic heritage) in Kent
'Argentina are dangerous'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Argentina are dangerous across the park. They gave New Zealand problems with their brutality in the first game. They've got some subtleties in the back line, too. They'll miss Marcelo Bosch, though."
Good luck boys
15 minutes till kick-off
Former Scotland international Rory Lawson wishes Ireland well and shares his predictions for the tournament.
'O'Connell's presence still counts'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Having Paul O'Connell around today does a lot for Ireland, even though he can't play. He's an icon of Irish rugby. The All Blacks did that with Tony Woodcock - he hasn't gone home either. Having players around like that is an inspiration. Just having him there, knowing he's watching, knowing how high his standards are, can make a difference."
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O'Connell forced to watch on
Ireland v Argentina (13:00 BST)
The Millennium Stadium is gradually filling up, fans leaving the bars, sipping the remaining dregs from their pints, to find their precious seats.
Paul O'Connell, hobbling on crutches, is on the sidelines, chatting and watching his team-mates warm up. He's been there for quite a while. They might have to drag him from the pitch.
Oh what would he give to be going into battle with his band of brothers today.
Ireland gigantic task
Ireland v Argentina (13:00 BST)
Argentina team news
Ireland v Argentina (13:00 BST)
Suspended centre Marcelo Bosch is the only regular name missing from the Argentina line-up, having been banned for a week for committing a dangerous tackle against Namibia in Argentina's final pool game.
He is replaced by Matias Moroni, one of 10 changes made by Argentina coach Daniel Hourcade for the Ireland game.
Many of the leading players rested for the Pool C game against Namibia return, with scrum-half Martin Landajo starting ahead of Tomas Cubelli to win his 50th cap.
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Wales' capital has turned green for the afternoon. But that isn't to say there are a number of Pumas lurking around the streets and, as we know from previous games in this tournament, Argentina fans know how to turn up the volume. They have plenty of bite those Puma fans.
Ireland team news
Ireland v Argentina (13:00 BST)
John Haughey
BBC Sport at the Millennium Stadium
"Where to start with Ireland? Johnny Sexton was ruled out on Saturday morning because of what was described as an abductor muscle injury. More commonly known as a groin strain, I think.
"Ian Madigan, who came on for the injured fly-half after 26 minutes last weekend, replaces Sexton.
"Iain Henderson replaces hamstrung Paul O’Connell at lock, with Chris Henry and Jordi Murphy taking over from injured Peter O’Mahony and banned Sean O’Brien in the back row."
Live Reporting
Aimee Lewis
All times stated are UK
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Pumas enjoy biggest win over Ireland
Ireland 20-43 Argentina
Argentina have now beaten Ireland in three of the four World Cup meetings between the sides, but this 23-point winning margin was the Pumas' biggest against Ireland in Test rugby.
The Pumas were impressive, attacking with verve, and clinical when the tryline loomed. They will, you assume, be oozing confidence in the semi-finals, whoever their opponents will be, be it Australia or Scotland.
Talking of which. The last semi-final of this tournament will start in under 30 minutes and live coverage of the Twickenham encounter has already started which means it's time to shut down this live commentary.
To join my colleague Mike Henson, who will guide you through the match, simply click here. Bye for now.
'It's an Australia-New Zealand final'
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"I think the two form teams are Australia and New Zealand. I think they will contest the final. The winner will be whoever takes their opportunities."
'We tried too hard and got loose'
Ireland 20-43 Argentina
Ireland coach Joe Schmidt: "The result just reflected the tour de force demonstrated by the southern hemisphere teams this weekend. We didn't get the start we wanted, but I'm incredibly proud of how we got back into the contest. When you try a bit too hard, you get loose, and they have tremendous speed merchants to take advantage. It was always going to be disappointing if we lost, but it was exacerbated in those final 15 minutes."
Felicidades Pumas!!!!
Barcelona and Argentina midfielder Javier Mascherano is also enjoying the moment.
'This is just the start for Argentina'
Ireland 20-43 Argentina
Matt Dawson
2003 World Cup winner on BBC Radio 5 live
“The consistency of performance is always key to success, and I also believe Argentina have some real game-breakers - players such as Tuculet, Imhoff, Cordero. They have probably learned from playing in Europe and playing in the Rugby Championship. There’s talk of them getting a Super 15 franchise too, so this is just the beginning for Argentina."
The Hand of God calling
Ireland 20-43 Argentina
Leicester Tigers forward Jordan Crane tells Argentine football great Diego Maradona to book those flights to London.
The World Cup-winning football captain did, after all, say he would come over to support the Pumas again should they reach the semi-finals. Well, Diego, your boys did it.
Los Pumas!
Ireland 20-43 Argentina
Manchester City's Pablo Zabaleta gets all patriotic on us...
'Defence the difference'
Ireland 20-43 Argentina
Argentina wing Juan Imhoff, speaking to ITV Sport: “We will enjoy this moment but we know we have a tough game next week. Ireland played with a great intensity. We are a really good team in offence. But today we had a defence to make the difference.”
Pumas still celebrating
Ireland 20-43 Argentina
Argentina's players are, understandably, still celebrating on the Millennium Stadium turf. Their fans have also stayed behind to soak it all up.
Juan Martin Fernandez Lobbe is accompanied by his children (I think) and is posing for a picture with his two toddlers with the scoreboard in the background. A never to be forgotten moment.
Clarke 'gutted'
Ireland 20-43 Argentina
Former Open golf champion Darren Clarke is magnanimous in defeat.
Sanchez the leading man
Ireland 20-43 Argentina
Argentina outside-half Nicolas Sanchez was named man of the match for brilliantly orchestrating his backline and collecting 23 points. He is also now the leading scorer at this World Cup.
'Argentina took their chances'
Ireland 20-43 Argentina
Ireland captain Jamie Heaslip to ITV Sport: "It's very disappointing to lose in such a big game. We didn't help ourselves at the start. We came back into it but we gave ourselves too much to do. This is a special group of players and a special group of fans.
"Argentina played a very expansive game. They stretched us. They took their chances. We got back to within three points - but then they took their opportunities to kick on."
'Ireland's defence found out'
Ireland 20-43 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"It'll be a strange type of inquest because those 'What if?' questions will be there. There will be questions about their defence. They hadn't really been asked any questions in the pool stages. The back-line defence was found out. Argentina, a team with an all-round game, asked questions they couldn't answer."
'Ireland's execution wanting'
Ireland 20-43 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Ireland's execution let them down but you could not question their heart. Their execution was found wanting, while Argentina were ruthless. The northern hemisphere teams are competitive, but the southern hemisphere teams have finished when they've had the chance. They've not panicked. They've backed their skill sets. You have to take your chances when they are there."
'Done your country proud'
Golfer Rory McIlroy, a four-time major winner, has tweeted his thoughts about the match.
Argentina through to the semi-finals
Ireland 20-43 Argentina
So, the south gets the better of the north once again. For those wanting to know, the northern hemisphere has always had at least one representative in the semi-finals in each of the previous seven World Cups.
It was only France in 1999 - the only time no home nation made the last four - but every other staging has seen two northern hemisphere sides in the last four.
The north's hopes now rest with Scotland, who will take on Australia at 16:00 BST.
Ambitious, joyous, ruthless
Ireland 20-43 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"I wonder how many fans of European teams will still deny that northern hemisphere rugby is out of date? Argentina were playing a different brand of rugby to Ireland - ambitious, joyous, ruthless - and it was great to see it work.
"They have learned well from their southern hemisphere rivals after their short stint in the Rugby Championship, proving that you only improve by playing opponents better than you."
Full-time
Argentina show their class
Ireland 20-43 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"That try from Joaquin Tuculet has to go down as one of the finishes of the World Cup and also demonstrates one of the key differences between north and south - the ability to finish clinically, under intense pressure."
Full time: Ireland 20-43 Argentina
England's World Cup winning coach Sir Clive Woodward is impressed with the Pumas.
Full-time
Ireland 20-43 Argentina
There'll be no first World Cup semi-final for Ireland. Instead, it's Argentina who will play either Australia or Scotland. Ireland's players on their knees, distraught, but they were well beaten.
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Ireland 20-43 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"The better team won. You can't cough up 20 points in the opening 20 minutes of a World Cup quarter-final and expect to win. The fact they got back into contention will only frustrate them more. Ireland weren't precise enough, made some bad decisions and executed moves poorly."
Full-time
Ireland 20-43 Argentina
Ireland recycling. Rhys Ruddock gains some metres... Robbie Henshaw tries to sashay through Argentina's defence, but the Pumas are alert to his shuffling hips... Ireland, eventually, lose possession... and that's the end of the match.
Ireland 20-43 Argentina
Ireland hoping for one last hurrah before they depart this tournament. They earn a penalty 10m from Argentina's line, Jamie Heaslip thunders forward...
Ireland 20-43 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Argentina have played the last part of the second half so well that Ireland are lost for ideas. Ireland had a good spell of pressure early in the second half, but they haven't really been back into the opposing 22 since then. Argentina have won all of the big moments today."
Penalty - Sanchez
Ireland 20-43 Argentina
Keith Earls with a late shoulder-charge on Santiago Cordero, but he escapes with a warning, the centre smiles wryly. The result is a chance for Nicolas Sanchez to practice his kicking, not that he needs it, and he knocks it over with his usual aplomb.
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Ireland 20-40 Argentina
Wales centre Jamie Roberts is impressed.
Ireland 20-40 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Absolutely fantastic score. Ireland have looked vulnerable on the short side throughout the second half. Argentina have been probing, and they've found the way through with a superb try.
"You have to take your hat off to Argentina. They've taken a lot of punishment, absorbed it and come back. Ireland have made one or two critical errors, Argentina have seen their chance and taken it. And that is it, I'm afraid, for Ireland."
Converted try - Imhoff; Sanchez conv
Ireland 20-40 Argentina
Dear Argentina fans, you may celebrate, you are through to the semi-finals. Juan Martin Fernandez Lobbe punching holes, offloading to top-poacher Juan Imhoff and the winger has enough time for a swallow dive as he dives over.
Nicolas Sanchez, in front of the posts... two points.
Ireland 20-33 Argentina
Just the 10 minutes remaining and Ireland need to conjure a magic trick of Houdini standards if they are to escape from here. They have a mountain to climb, and it feels as if they have only brought flip-flops with them for the task.
Ireland 20-33 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"It was outstanding stuff from Argentina. The finishing was lethal."
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Ireland 20-33 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This all stems from Ireland not being able to clear their lines. They messed around with possession, and they're paying the price. They should have been up the pitch."
Converted try - Tuculet; Sanchez conv
Ireland 20-33 Argentina
Argentina are celebrating. Joaquin Tuculet thinks he's scored near the touchline. Has he?
It was fabulous build-up play from the Pumas, the forwards doing the damage before the backs were let free to dazzle and outwit Ireland by going wide.
Joaquin Tuculet steps inside Rob Kearney, and has the strength to touch down in the corner despite Irish bodies on his back.
And it's a stunning touchline conversion from Nicolas Sanchez from the touchline, inflicting the mortal blow.
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Anybody nervous?
Ireland 20-26 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This is just the time when Argentina might think Ireland are trying to play too much rugby now."
Ireland 20-26 Argentina
Pablo Matera, taking his eye off the ball, loses possession and could this be Ireland's chance? They need to be quick. They need to be clinical. But Robbie Henshaw stutters, going for the razzle-dazzle mis-pass when a simple through-the-hands move would have sufficed. Irish momentum dies a death.
Wallaby wants to know the score
Australia are on the way to Twickenham, but back rower David Pocock wants to know the score. Well seeing as you asked David, it's Ireland 20-26 Argentina, but it's close... and tense.
Ireland 20-26 Argentina
Ireland have just under 15 minutes to save their tournament. But Ian Madigan, feeling the pressure perhaps, kicks straight into touch. Fans groan in unison. The outside-half faltering under the spotlight.
Turnovers now level-pegging
Like Argentina in the first half, Ireland are now winning turnover ball with flanker Jordi Murphy leading the defensive effort.
Ireland 20-26 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"Another three points for Argentina. These little bits of indiscipline can be crucial."
Ireland 20-26 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Ireland paid for not clearing pressure. Conor Murray should have found touch and given Ireland a chance to restart. All of a sudden, Argentina have kicked another three points."
Penalty - Sanchez
Ireland 20-26 Argentina
Daylight now between Ireland and Argentina. Outside-half Nicolas Sanchez shooting as sharply as ever, adding three points to the scoreboard and, in the process, becoming the most ruthless collector of points in this tournament.
Ireland 20-23 Argentina
Joaquin Tuculet runs back with interest towards Ireland after collecting a high ball. The Pumas camped in enemy territory - and Devin Toner wraps an arm around the neck of the ducking Nicolas Sanchez and the referee has seen that.
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Ireland 20-23 Argentina
The penalty count has shot up for Argentina... Ireland certainly on the up whichever way you look at it.
They've secured turnover ball, only Conor Murray messes up, sending his pass into touch instead of Keith Earls.
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Missed penalty - Madigan
Ireland 20-23 Argentina
Ian Madigan trades power for accuracy, and his effort drifts wide. It would have been a mighty effort from near the half-way line had he succeeded. Twenty minutes remaining....
Ireland 20-23 Argentina
Conor Murray sets his backline rolling, but Keith Earls is swallowed up as Matias Moroni smothers him in the tackle.
Argentina with put-in at the scrum... Irish fans serenading their team... The Pumas not the dominant force they were in the scrum, but Martin Landajo darts from the base, on to Santiago Cordero but the wing loses the ball in contact.
Marcos Ayerza, a bull-like charge through the ruck to take out scrum-half Conor Murray and referee Jerome Garces has little option but to give Ian Madigan the chance to level.
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Can Ireland nick it?
Ireland 20-23 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"Argentina guilty of playing too much now, their half-backs need to take this game by the scruff of the neck or Ireland will nick this.
"I honestly can't remember the last time I was so nervous at a rugby match. And I'm not Irish, and I'm definitely not Argentine."
Ireland 20-23 Argentina
Both teams have made a raft of changes, too many to mention in one go. One replacement, Facundo Isa thundering down the blindside - but Ireland aren't prepared to fold.
Magnificent by Rory Best, the Ireland hooker securing the turnover ball in the next phase. And the crowd are whooping and haw-hawing.
Penalty - Madigan
Ireland 20-23 Argentina
Ramiro Herrera is still on the field, but he should be apologising to his team-mates. His folly in this match has proved costly. Ian Madigan drags Ireland to within three points of the Pumas.
Ireland 20-23 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Holy moly! We've seen it for the first time in the World Cup. Common sense has prevailed. There was no way that was a red card for Herrera."
Ireland 17-23 Argentina
Ramiro Herrera could be in trouble. The tight-head needs to smile sweetly here. He came charging in late into the ruck. Jerome Garces chats to his fellow officials, and he's let off with a penalty. "I give a penalty because you used your arm," says the referee. He could have seen red.
How's the heart, Brian?
Ireland 17-23 Argentina
Are you OK, BOD? The former Ireland centre appears to be struggling with the drama...
Ireland 17-23 Argentina
What an impact Luke Fitzgerald has made since coming on for Tommy Bowe.
He has run 57m, had two clean breaks, scored a try and set up Jordi Murphy's try with a wonderful run.
Argentina are missing tackles as a tidal wave of green comes at them, breaking the gain line.
Wingers Santiago Cordero and Juan Imhoff are the worst offenders having missed two tackles apiece.
Ireland 17-23 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"That was a big swing there. Ireland had a fantastic attacking platform and took a couple of wrong decisions. They have to convert those chances. It was great defensive work by Argentina, though, and they've got down the pitch to get the three points and just calm things down."
Penalty - Sanchez
Ireland 17-23 Argentina
Argentina, though, in the line of fire turnover ball in the shadow of their posts... Juan Imhoff comes roaming from wide, the winger caught just before he could do some serious damage, but Ireland are penalised at the breakdown and Nicolas Sanchez stops the rot.
Ireland 17-20 Argentina
It's all Ireland in these last few minutes. Ireland's fans are roaring. Rory Best finds his man in the line-out... the men in green roaming around Argentina's 22m... the centres punching holes in midfield... wave after wave of green crushing towards Argentina's defensive line.
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Ireland 17-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"What I liked about Ireland's last try was that they just gave the ball to Luke Fitzgerald a little earlier. Sometimes, they've tried to give the ball right on the advantage line, and they've found an opponent coming in at the same time. Instead, let them use their footwork to get over the advantage line. Fitzgerald got the ball early and bust the tackle to set up Murphy."
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Ireland 10-20 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"It is absolute bedlam in the Millennium Stadium, difficult to remember a noise like it. This could well carry Ireland to victory.
"Every Ireland charge, every Argentina mistake, every little thing that goes Ireland's way is greeted with ear-splitting roars. We have a grandstand finish on our hands..."
Ireland 17-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Luke Fitzgerald has brought Ireland back into this game with two fantastic breaks. Working that line-out, he stepped the defender and Jordi Murphy took it on for the try. What a game we have now."
Converted try - Murphy; Madigan conv
Ireland 17-20 Argentina
A honeyed platform for Ireland's backs from the line-out... Replacement Luke Fitzgerald the architect of the try, breaking loose from one tackle, evading the attention of Santiago Cordero and slipping the ball to the onrushing Jordi Murphy, who barges over the line.
Paul O'Connell, eyes like saucers, punches the air from the sidelines.
Ian Madigan adds the extras. Ireland have come out firing.
Ireland 10-20 Argentina
Dan Tuohy
Ireland second row on BBC Radio Ulster
"Ireland have got to get the first score after half-time - even if it's only a penalty to make it a one-score game. Ireland must up the intensity now."
Ireland 10-20 Argentina
Argentina start this half as they did the first, on the front foot, on Ireland's 22m. But Ireland are savvy at the breakdown. Flanker Chris Henry scavenging, stealing the ball with success and allowing Ian Madigan to ease the pressure with a touchfinder.
Kick-off
Ireland 10-20 Argentina
Thirty players are on the pitch. There's one referee, too. They're battered and bruised, shirts muddy, but they're ready for another 40 minutes.
We're off. By the way, no team has fought back from a 10-point deficit to win a knockout game.
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The simple way of choosing sides as a neutral....
Keep the faith!
Ireland 10-20 Argentina
Ireland maybe 10 points behind at half-time but Irish fans must stay calm and, like comedian Johnny Vegas, keep the faith.
'Pumas performance not a surprise'
Ireland 10-20 Argentina
Ireland 10-20 Argentina
Ryan Constable
Former Australia centre on BBC Radio Ulster
"Ireland have found a way to get back into the game and are now competing at the breakdown. After their dreadful start, they will feel 10 points down is not an insurmountable deficit at half-time."
Half-time
Ireland 10-20 Argentina
In terms of territory and possession it was even in the first half. Ireland enjoying 53% of possession and 56% of territory as they fought their way back from a 20-3 deficit.
Tackles? Ireland have made 64, while Argentina have made 56.
But it's in the metres made that we find a gaping difference between the sides (Ireland 185m, Argentina 308m).
Ireland 10-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Let's break this down: Who's the most disappointed changing room right now? Absolutely Argentina - despite their lead. Ireland weren't in the game for 20 minutes, but now they are. Argentina will be disappointed they haven't capitalised on being 20-3 up in a World Cup quarter-final. They threw the kitchen sink at Ireland, and could have had this game almost in the bag by half-time."
Ireland's fan power
Ireland 10-20 Argentina
Ben Dirs
BBC Sport at the Millennium Stadium
"The Irish not out of this yet, this crowd could yet be a factor, it's ferocious when Ireland are attacking."
Ireland 10-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I get the sense that Ireland are coming back into it. But some of their decision making is a little bit off. They're taking complicated options when the simpler choice is better."
Half-time
Ireland fight back after Argentina's blistering start
Half-time
Ireland 10-20 Argentina
Juan Imhoff, Argentina's prime poacher, with ball in hand on the left wing, but Ireland's defence are alert and the winger is ejected into touch.
Ireland secure on their own line-out ball and Conor Murray concludes a glorious half. Boot to ball, into touch.
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Ireland 10-20 Argentina
Ireland upping the ante at the breakdown as Argentina rumble around their 22m line. Cian Healy makes amends for his transgression at the scrum, slowing down play, and the Pumas are penalised for failing to stay on their feet. The pressure valve loosens a tad.
Ireland 10-20 Argentina
Super stuff from Matias Moroni, holding up a man in green in the tackle, gaining his team a scrum on the halfway line. Silly from Ireland, letting momentum slip.
From bad to worse. Ireland loose-head prop Cian Healy nose to the ground, and Jerome Garces has little option but to present Nicolas Sanchez with a chance to boot Argentina into Irish territory.
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Ireland 10-20 Argentina
Five minutes until the break and Ireland's forwards are rumbling, pushing Argentina's defence back inch by inch. But Argentina turnover ball this time just when the backs are set in motion. Winger Dave Kearney the man caught isolated on the floor.
Missed penalty - Madigan
Ireland 10-20 Argentina
Ireland's scrum is tree trunk still after wobbling in the opening minutes. Keith Earls running straight in midfield, but men in green get no joy so the referee halts play and penalises the Pumas for collapsing at the scrum.
Ian Madigan steps up, but his effort hits the uprights!
Ireland 10-20 Argentina
Ireland have stemmed the blue tide and have pulled themselves back into the game.
Argentina are seeing less of the ball and their frustration is leading to penalties.
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Ireland 10-20 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"The main difference over the last 12 minutes or so is that Argentina haven't been able to get their hands on the ball and get some rhythm. They were using it well, so at least Ireland have stopped that."
Ireland 10-20 Argentina
Ireland, pride pricked, are fighting their way back into the light, but they're now facing 15 men as Ramiro Herrera's sin bin is over.
Ian Madigan needs the attention of the medical staff. The Millennium Stadium turf turning into a scene of a Hollywood war epic.
But the outside-half is not going to leave this field because of a bone-crunching collision with Nicolas Sanchez. He's craving a leading role.
Converted try - Fitzgerald; Madigan con
Ireland 10-20 Argentina
Conor Murray collects Santiago Cordero's kick ahead, and Ireland punish the winger's loose kick. Robbie Henshaw finds replacement Luke Fitzgerald and the winger steps in from the touchline and, with an enchanting change of pace, touches down, presenting Ian Madigan with an easy conversion.
Missed penalty - Sanchez
Ireland 3-20 Argentina
Argentina bossing the breakdown, and nearly every call is going their way. Nicolas Sanchez falters this time, though, but hang on... what's happening here...
Ireland 3-20 Argentina
A rare mistake from a man in blue and white. Juan Martin Hernandez, the centre with usually regal hands, knocks on to gift Ireland a put-in at the scrum on the halfway line.
How will Ireland's forwards fare? Argentina are down to 14 men so the Irish scrum is firm but Robbie Henshaw loses possession just as the men in green prepare to spin it wide.
Ireland 3-20 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I'm worried about the options Ireland are taking. They're making too many wrong decisions. Sometimes, for instance, Conor Murray has gone right when the options are left. When you're making wrong decisions, it's usually a sign that your head's not right, and Ireland just aren't there."
Pumas impressing
Current players loving Argentina
Ruthless!
Penalty - Sanchez
Ireland 3-20 Argentina
Ireland need to make the most of their man advantage, but they can't do anything without the ball. Argentina resolute in defence, dashing in attack.
Flanker Chris Henry is caught coming in at the side of the ruck and Nicolas Sanchez inflicts further damage in a dreamy start for the Pumas.
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Ireland 3-17 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"This is a chance Ireland have to take. They have to capitalise on the fact that Argentina are a man down. If they can't capitalise, it will be such a boost for Argentina.
"Argentina want to run the clock down. That's what you do when you're a man down."
Penalty - Madigan
Ireland 3-17 Argentina
Ireland make the most of their opportunity. A neat touchfinder takes them to within 10m of Argentina's line and the Pumas crumble under the pressure, giving Ian Madigan a shot at goal in front of the posts. It's the sort of kick he could rattle off in his sleep.
Sin-bin - Herrera
Ireland 0-17 Argentina
Could that be the moment which swings the pendulum in Ireland's way. Ramiro Herrera with a late tackle on Keith Earls. The Irish fans in the crowd hiss when they see the replay. The prop is off. He can rest for 10 minutes
Ireland 0-17 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"I'm very worried. Ireland are really struggling at the breakdown. They're not making an impact in the rucks. Argentina are able to recycle the ball quickly, and Ireland can't get on the front foot."
Ireland 0-17 Argentina
Argentina threatening whenever they have the ball. Number eight Leonardo Senatore thunders down the left wing, then Juan Martin Fernandez Lobbe makes hard yards in the middle of the field.
The Pumas in opposition territory at lighting speed. Nicolas Sanchez eyes up the drop-goal, but, oof, it's an ugly one. It hasn't the height nor the distance and it wobbles limply wide.
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The north-south divide debate is rearing its ugly head on #bbcrugby...
'Worrying times for Ireland'
John Haughey
BBC Sport NI at the Millennium Stadium
"Stephen Ferris said during the week that he would be a bit worried if Argentina went six or 10 points ahead early on. Make that 17 Stevie, ouch."
Penalty - Sanchez
Ireland 0-17 Argentina
As Tommy Bowe was stretchered off, Ireland fans may have forgotten that their team was penalised leading up to that injury. Unfortunately for the Irish, Nicolas Sanchez is in ruthless mood, knocking a penalty over from 43m with aplomb.
Ireland 0-17 Argentina
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"The big difference between the two forward lines is Argentina are playing on the gain line and Ireland are playing in the transition zone. Ireland need to galvanise. They need to reassess their game plan and find a way to make sure they don't lose this game in the first half.
"Ireland have to retain the ball, get patient and get physical."
Ireland 0-14 Argentina
Tommy Bowe runs into Tomas Lavanini and the winger falls to the floor, face contorted in pain, as if he's run into the path of a tank at full speed, which I suppose he has.
The mobile stretcher comes on. It could be the end of the former Ospreys man's afternoon. Applause for Bowe as he leaves the pitch.
Ireland 0-14 Argentina
It has been ALL Argentina so far.
The Pumas have run 145m with the ball, 123m more than Ireland.
Argentina have been trying to get the ball out wide and are playing an expansive game with right winger Santiago Cordero seeing plenty of action.
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Ireland 0-14 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Argentina are playing all the rugby. They're moving the ball around and Ireland are on the rack here."
Converted try - Imhoff; Sanchez conv
Ireland 0-14 Argentina
Argentina punching holes in midfield... Ireland's defence in disarray.
Santiago Cordero with a well-weighted crossfield kick from the wing and his fellow flyer Juan Imhoff reads the play beautifully, sprinting towards the posts and grabbing the ball and touching it down before it goes dead.
Fortune favours Nicolas Sanchez, the outside-half's conversion rattles the posts before falling the right side.
Ireland 0-7 Argentina
An intense opening to this match. Argentina fired up and their forwards breathing fire, pushing Ireland back in the scrum. Ireland's set-piece crushed on their own put-in. Only the second time they've lost their own scrum in this tournament.
Ireland 0-7 Argentina
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"Great score from Argentina. They took Ireland through a couple of phases and found space on the outside. I was worried that Ireland's defence hadn't been tested so far in this tournament - and now we have the answer there. Ireland need to get on the scoreboard now, with a penalty, a drop-goal, anything. They look off the pace."
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Converted try - Moroni; Sanchez con
Ireland 0-7 Argentina
What a score! Joaquin Tuculet gathers the high ball, getting his men rolling forward. Brilliant from Santiago Cordero, who sucks in Rob Kearney and sets Matias Moroni free to gallop down the right wing.
Nicholas Sanchez as reliable as ever, adding two points from near the touchline.
Ireland 0-0 Argentina
The Pumas keeping ball in hand before Nicolas Sanchez changes ploy, boot to ball, but Rob Kearney passes his first test. Ireland on the front foot, but Agustin Creevy brilliantly steals possession. Although, the Pumas fail to find touch from the resultant penalty.
This could be close!
but not as close as Ian Madigan's new haircut
The Ireland fly-half, in for the injured Johnny Sexton, has marked the occasion with the shortest of short back and sides.
Kick-off
Ireland 0-0 Argentina
Jerome Garces is the man in charge of keeping order for the next 80 minutes. He blows his whistle. Ian Madigan kicks it to Tomas Lavanini and it's safe to say this cracker has started.
Post update
Ben Dirs
BBC Sport at the Millennium Stadium
"The Irish have found full voice now, 'The Fields of Athenry' ringing out around the Millennium Stadium. But what's this? The Argentines quickly drown them out with some songs of their own. It's already epic in Cardiff, and we haven't even kicked off yet. Stand by for a classic."
National anthems
Ireland v Argentina (13:00 BST)
Oh my, the salty tears are flowing from Argentina's players even before their national anthem kicks into full swing. It's as if someone's put a picture of their deceased childhood pets up on the big screen.
Next it's Ireland's turn to add their voice to proceedings and the men in green win the singing contest. Paul O'Connell singing along from the stands, standing with the aid of crutches.
Stirring stuff.
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Five minutes until kick-off
Ireland v Argentina (13:00 BST)
Cries of "ole!" rings around the Millennium Stadium, both sets of fans creating a crackling atmosphere.
The two teams in the bowels of the stadium, awaiting their call to march out from under the tunnel and into a wall of noise.
'Ireland win would be good for the game'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"It would be good for the tournament if Ireland made the semi-finals. If the last four are all southern hemisphere teams, that makes it more difficult.
"But it's not the end of the world for rugby union of there are no northern hemisphere teams in the semi-finals, though, because the best teams need to win. I think this has been the most competitive Rugby World Cup I've seen, and that's great for the game."
'Think France 20 years ago'
Ireland v Argentina (13:00 BST)
Denis Hickie
Former Ireland winger on BBC Radio 5 live
"One of my best rugby memories is in 2003, at the Adelaide Oval, when we beat Argentina to make it through the pool stages at their expense. One of my worst memories is 2007, when Argentina knocked us out.
"Argentina were just better than us that day. This team are slightly different. There's more to Argentina's game now. People ask: How do Argentina play? Think France 20 years ago. They've a big strong pack and a huge willingness to move the ball. They're a very well balanced side."
The king's speech
Ireland v Argentina (13:00 BST)
John Haughey
BBC Sport at the Millennium Stadium
"Paul O’Connell is not going to be on the pitch for Ireland but his former team-mate and BBC Sport NI columnist Stephen Ferris is expecting the big man to play a role in rallying the troops before today’s game.
"The Munster legend's speeches regularly bring tears to the eyes of team-mates so goodness knows what Paulie has planned for today’s occasion as Ireland aim to qualify for a first ever World Cup semi-final."
'Ireland should be massively confident'
Ireland v Argentina (13:00 BST)
Ireland lock Dan Tuohy on BBC Radio Ulster: “As was the case in the first two quarter-finals, physicality around the breakdown is probably going to decide the outcome today but I think Ireland should still be massively confident despite all their injuries and Sean O’Brien’s ban.”
Ireland looking for six in a row
Ireland v Argentina (13:00 BST)
Argentina's last win against Ireland was in the 2007 World Cup when they won 30-15 in the group stages.
But since then the Pumas' record against the Irish reads played five, lost five. Should the Irish take heart from that?
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'Argentina are dangerous'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Argentina are dangerous across the park. They gave New Zealand problems with their brutality in the first game. They've got some subtleties in the back line, too. They'll miss Marcelo Bosch, though."
Good luck boys
15 minutes till kick-off
Former Scotland international Rory Lawson wishes Ireland well and shares his predictions for the tournament.
'O'Connell's presence still counts'
Ireland v Argentina (13:00 BST)
Justin Marshall
Former New Zealand scrum-half on BBC Radio 5 live
"Having Paul O'Connell around today does a lot for Ireland, even though he can't play. He's an icon of Irish rugby. The All Blacks did that with Tony Woodcock - he hasn't gone home either. Having players around like that is an inspiration. Just having him there, knowing he's watching, knowing how high his standards are, can make a difference."
O'Connell forced to watch on
Ireland v Argentina (13:00 BST)
The Millennium Stadium is gradually filling up, fans leaving the bars, sipping the remaining dregs from their pints, to find their precious seats.
Paul O'Connell, hobbling on crutches, is on the sidelines, chatting and watching his team-mates warm up. He's been there for quite a while. They might have to drag him from the pitch.
Oh what would he give to be going into battle with his band of brothers today.
Ireland gigantic task
Ireland v Argentina (13:00 BST)
Argentina team news
Ireland v Argentina (13:00 BST)
Suspended centre Marcelo Bosch is the only regular name missing from the Argentina line-up, having been banned for a week for committing a dangerous tackle against Namibia in Argentina's final pool game.
He is replaced by Matias Moroni, one of 10 changes made by Argentina coach Daniel Hourcade for the Ireland game.
Many of the leading players rested for the Pool C game against Namibia return, with scrum-half Martin Landajo starting ahead of Tomas Cubelli to win his 50th cap.
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Wales' capital has turned green for the afternoon. But that isn't to say there are a number of Pumas lurking around the streets and, as we know from previous games in this tournament, Argentina fans know how to turn up the volume. They have plenty of bite those Puma fans.
Ireland team news
Ireland v Argentina (13:00 BST)
John Haughey
BBC Sport at the Millennium Stadium
"Where to start with Ireland? Johnny Sexton was ruled out on Saturday morning because of what was described as an abductor muscle injury. More commonly known as a groin strain, I think.
"Ian Madigan, who came on for the injured fly-half after 26 minutes last weekend, replaces Sexton.
"Iain Henderson replaces hamstrung Paul O’Connell at lock, with Chris Henry and Jordi Murphy taking over from injured Peter O’Mahony and banned Sean O’Brien in the back row."