Match ends, Chelsea 0, Arsenal 0.
Chelsea manager Antonio Conte backed the video assistant referee (VAR) system after his side's goalless draw with Arsenal in their Carabao Cup semi-final first leg.
Referee Martin Atkinson consulted the VAR on two Chelsea penalty claims, when Victor Moses tangled with Ainsley Maitland-Niles in the first half and for Danny Welbeck's last-minute challenge on Cesc Fabregas, but he was satisfied enough with the evidence relayed to him not to award a spot-kick.
"I am very positive about VAR because when there is a big doubt during the game it is right the referee and the other referee watch the video to check and make the best decision," Conte said.
"I think everyone wants less mistakes during the game and I think this could be very positive for sure."
The two sides will meet in the second leg at Emirates Stadium on 24 January after Arsenal showed resilience following Sunday's FA Cup third-round defeat by Nottingham Forest to frustrate a strong Chelsea team.
"It was a good performance," Gunners manager Arsene Wenger said.
"We were well organised. It was a good draw and we have to finish the job."
Arsenal were the beneficiaries of careless Chelsea finishing, with Fabregas and Andreas Christensen culprits with poor headed efforts, while keeper David Ospina saved well from Moses and Alvaro Morata.
Alexandre Lacazette blazed Arsenal's best chance over the bar in the first half but there was no doubt they were happier with the result to set up the second leg at Emirates Stadium.
The VAR revolution continues
After making its debut in Monday's FA Cup third-round tie between Brighton and Crystal Palace, the video assistant referee was once again used at Stamford Bridge - and it provided moments of frustration, confusion and tension.
Referee Atkinson consulted it to adjudicate a first-half incident before a set-piece when Chelsea's Cesar Azpilicueta clashed with Calum Chambers, eventually lecturing the pair, and again when Maitland-Niles tumbled under a challenge from Moses.
It resulted in a brief delay, with Arsenal's fans chanting "VAR", before Atkinson stuck with his original decision - but there was an anxious moment for Arsenal in the closing minutes when Welbeck made a tackle which needed to be perfectly timed in the area on Fabregas.
It was then when another sight that will be become increasingly familiar was witnessed, with Chelsea manager Conte effectively appealing to fourth official Jon Moss for VAR by making the shape of a television screen.
A long delay, some would argue too long, ensued before Atkinson delivered what was clearly the correct decision - no penalty.
"You have to improve and understand that when you start to use VAR you then need to add more extra time," Conte said. "When there are doubts about two situations in the game then the extra time is seven, eight or nine minutes."
Wenger added: "It was interesting. It was a cause of anxiety as it took a bit of time to make the second decision with Welbeck and Fabregas, but overall it worked well.
"But between the penalty action or penalty not action, with the time taken it would have been strange to come back to the penalty."
Chelsea wasteful as Arsenal hold firm
Chelsea had the opportunities to build an advantage for the second leg - but found Arsenal in resilient mood and wasted the chances that presented themselves.
Arsenal needed a show of strength after Sunday's embarrassing FA Cup exit to Nottingham Forest and showed steel, with Shkodran Mustafi and Calum Chambers excellent in defence.
Fabregas wasted a clear headed chance in the first half, while Christensen was also profligate - which led to frustration for manager Antonio Conte and an animated discussion with the match officials after the final whistle.
Full-time in this low-key game was greeted with virtual silence by Chelsea's fans.
Chelsea's quality is such that they have certainly not missed their chance but their carelessness means they have made life more difficult for themselves when they travel to Arsenal in a fortnight.
"We are about 50/50 because don't forget not to concede a goal at home could be very important for the second leg," Conte said.
"At the same time we know that to play at Emirates Stadium is not easy but we are ready."
Wilshere's new injury worry
Jack Wilshere's recent rejuvenation and return to fitness was rewarded with the captain's armband for this match.
The England midfielder has started seven of Arsenal's last nine games and his elevation to the captaincy was warmly greeted by Gunners fans, who always reserve special affection for the 26-year-old, on social media.
Sadly, after a performance which illustrated Wilshere's growing confidence and authority, it ended with the familiar sight of him limping off through injury midway through the second half.
Wilshere was relishing his responsibility, pointing team-mates into position and directing operations from midfield, when a freak incident appeared to cause his latest problem.
He stretched to block an attempted long pass from Chelsea's Danny Drinkwater which struck him on the foot, seeming to twist his ankle.
Wilshere tried to continue after treatment but it was to no avail and he was soon removed from the action to have an ice pack applied.
Wenger will hope the problem is not serious as recent weeks have proved Wilshere is still capable of influence in his side - and perhaps even with England once more if he can put together a sequences of games.
Wenger living every moment - from the press box
Arsene Wenger's technical area ban meant he had to decamp to the Stamford Bridge press box to observe the action from among the ranks of the media.
Flanked by a security man and former keeper Jens Lehmann, now a member of Arsenal's backroom team, it provided an intriguing close-quarters insight into the range of emotions managers run throughout such a big game.
Wenger remained relatively calm, even when Lacazette wasted a presentable first-half chance, only rising from his seat once during the game when Welbeck was penalised for a foul on Moses, but it was also easy to detect the strains and stresses.
He banged the table in front of him when Granit Xhaka committed a foul against Eden Hazard, shifted constantly in his seat, throwing back his head in frustration when opportunities came and went, such as Lacazette getting carelessly caught offside and when a promising free-kick position was wasted.
As he left his seat at the final whistle, though, Wenger will have been a satisfied man. Arsenal are right in this tie.
Man of the match - Calum Chambers
A rare blank for Chelsea - the stats
- Chelsea have now failed to score in just three home games in all competitions under Antonio Conte - all of them have been this season and two have been against Arsenal.
- Indeed, Arsenal are only the second team to keep two clean sheets away at Chelsea in the same season, after Manchester United in 1998-99.
- The Blues have had consecutive goalless draws in all competitions for the first time since November 2012.
- All four meetings between these sides in all competitions this season have ended level - the last time two Premier League teams drew four games against each other in the same season was Blackburn v Sunderland in 2002-03.
- Chelsea have progressed on each of the three occasions they have drawn the first leg of a League Cup semi-final - against Manchester United in 2005, Wycombe in 2007 and Liverpool in 2015.
- Meanwhile, Arsenal have progressed just once from the three previous occasions they have drawn the first leg - going through against Tottenham in 2007, but failing against Aston Villa in 1996 and Tottenham in 2008.
Third-placed Chelsea return to Premier League action this weekend when they host Leicester on Saturday (15:00 GMT). Arsenal, who are sixth, travel to Bournemouth on Sunday (13:30 GMT).
- 6DrinkwaterSubstituted forWillianat 68'minutes
- 7KantéBooked at 79mins
- 10E HazardSubstituted forBakayokoat 84'minutes
- 9MorataSubstituted forBatshuayiat 87'minutes
- 30David Luiz
- 37dos Reis Carvalho
- 29XhakaBooked at 51mins
- 10WilshereSubstituted forElnenyat 57'minutesBooked at 86mins
- 9LacazetteSubstituted forSánchezat 66'minutes
- Martin Atkinson
- Shots on Target
Second Half ends, Chelsea 0, Arsenal 0.
Foul by Andreas Christensen (Chelsea).
Alexis Sánchez (Arsenal) wins a free kick in the defensive half.
Willian (Chelsea) wins a free kick in the attacking half.
Foul by Ainsley Maitland-Niles (Arsenal).
Attempt missed. Michy Batshuayi (Chelsea) header from the left side of the six yard box is high and wide to the left. Assisted by Tiemoué Bakayoko following a corner.
Attempt missed. Tiemoué Bakayoko (Chelsea) header from the centre of the box misses to the left. Assisted by Cesc Fàbregas with a cross following a corner.
Corner, Chelsea. Conceded by Granit Xhaka.
Substitution, Chelsea. Michy Batshuayi replaces Álvaro Morata.
Mohamed Elneny (Arsenal) is shown the yellow card for a bad foul.
Álvaro Morata (Chelsea) wins a free kick in the attacking half.
Foul by Mohamed Elneny (Arsenal).
Attempt saved. Granit Xhaka (Arsenal) left footed shot from outside the box is saved in the bottom left corner. Assisted by Alex Iwobi.
Attempt blocked. Mohamed Elneny (Arsenal) right footed shot from outside the box is blocked. Assisted by Alexis Sánchez.
Substitution, Chelsea. Tiemoué Bakayoko replaces Eden Hazard.
Foul by Willian (Chelsea).
Alexis Sánchez (Arsenal) wins a free kick in the attacking half.
N'Golo Kanté (Chelsea) is shown the yellow card for a bad foul.
Foul by N'Golo Kanté (Chelsea).