Match ends, Southampton 1, Chelsea 4.
Chelsea manager Frank Lampard says his Blues side can get "a lot better" after they swept past Southampton to move up to fifth in the Premier League.
Tammy Abraham's looping finish from Callum Hudson-Odoi's pass gave the visitors the lead, before Mason Mount doubled Chelsea's advantage from close range.
Danny Ings reduced the arrears from Yan Valery's cut-back, but N'Golo Kante's deflected effort off Pierre-Emile Hojbjerg and Michy Batshuayi's neat finish put the seal on a comfortable victory for Lampard's side.
"I didn't think we started that well, even though doing so had been something we'd talked about before," said the former England midfielder. "[Abraham's] goal came at the right time and after that I felt pretty comfortable.
"Getting four away from home - we're scoring - so it's a nice afternoon.
"Let's not get carried away, it's a long season and we feel we might have picked up more points than we've actually got. We've not been at our absolute best and we can be a lot better.
"We shouldn't be sloppy, and after going 2-0 up we should make it 3-0. We're scoring goals, but can we tighten up? Yes."
Plain sailing for in-form Blues
After a stuttering start to the campaign, there are signs that this youthful Chelsea side are beginning to build up a head of steam under Lampard.
This was the Blues' fourth successive win in all competitions - a result which lifts them level on points with fourth-placed Leicester City and only two behind champions Manchester City, who lost 2-0 at home to Wolves.
Youngsters Abraham and Mount have taken the top flight by storm after spending last season on loan at Aston Villa and Derby County respectively, and the duo were heavily involved here as the visitors raced into an early lead.
Hudson-Odoi - making his first league start under Lampard - sent a long ball over the top of the Southampton defence and Abraham was first to it, his looping finish over Gunn crossing the line before Yoshida could clear the ball to safety.
Chelsea capitalised on a poor piece of Southampton defending to double their lead seven minutes later, Mount latching on to Willian's precise pass before slamming home his fourth goal of the campaign.
There appeared to be no way back for the Saints at that stage as Chelsea continued to lay siege to the home goal, but Ralph Hasenhuttl's side pulled a goal back out of nothing when Valery wriggled his way past several Blues defenders before setting up Ings, who was left with an easy finish.
There was an element of fortune about Chelsea's third - Kante's speculative drive deflecting off Hojbjerg and wrong-footing Gunn - but the dominant visitors could have won by a higher margin.
Hudson-Odoi was thwarted by Gunn four minutes after the restart, before Batshuayi eventually completed the scoring in the final minute of normal time with a confident finish from Christian Pulisic's through-ball.
"It's a transitional team but we don't have that in our heads," Mount told Match of the Day afterwards. "We want to get as high in the table as we can.
"A lot of the young boys around us have played together for a long time. It's good having these boys around you in the senior team - it's a massive achievement and now we're looking forward to the international break."
Sloppy Saints leave Hasenhuttl with plenty to ponder
The last time Southampton suffered five defeats in their opening eight league games, they were relegated from the Premier League.
Hasenhuttl reverted to a four-man defence at St Mary's, with Ryan Bertrand dropping to left-back and Yan Valery replacing the absent Jannik Vestergaard.
The tactical switch did little to solidify the Saints' rearguard, however. Nathan Redmond sent a dipping effort inches over Kepa Arrizabalaga's crossbar within the opening minute, but it proved to be a false dawn for the hosts as Chelsea quickly gained a stranglehold on proceedings.
Southampton were culpable in their own downfall, giving the ball away on numerous occasions in the first half in particular. Indeed, it was Jan Bednarek's poor header to Oriol Romeu which gifted Chelsea possession in the build-up to Mount's goal.
Ings' clinical finish from Valery's cut-back appeared to spark the hosts briefly into life. Redmond fired into the side-netting from a tight angle and Ings also had a goal-bound effort blocked, but their self-belief drained away with Kante's deflected effort shortly before the break.
With games against Wolverhampton Wanderers, Leicester City and Manchester City coming up, it is hard to see where Southampton's next victory is going to come from.
Man of the match - Jorginho (Chelsea)
No home comforts for Southampton - the stats
- Southampton have lost three consecutive Premier League games for the first time since October 2018, under Mark Hughes.
- Chelsea have won each of their last four games in all competitions, equalling the longest win streak of Frank Lampard's managerial career to date (four games in August-September 2018 with Derby).
- This was Southampton's heaviest defeat in a home Premier League game under Ralph Hasenhuttl. Indeed, the last time they lost by three or more goals in a home game in the competition was also against Chelsea (0-3 in October 2018).
- Chelsea have scored three or more goals in three consecutive Premier League away games for the first time since August 2009.
- Southampton have won just one point in Premier League home games this season (P4 W0 D1 L3) - the fewest in their opening four home games of a top-flight campaign since 2001-02 (also one point).
- Tammy Abraham has scored nine goals for Chelsea across all competitions in 2019-20, the joint-most of any current Premier League player (along with Raheem Sterling).
- No player in the top four tiers of English football has scored more league goals than Chelsea's Tammy Abraham in 2019 (20 - joint-most with Sergio Aguero, Teemu Pukki and James Collins).
- Chelsea's Mason Mount has scored three goals in four away appearances in the Premier League this season, as many as he managed in 20 away league games under Frank Lampard at Derby last season (including play-offs).
'We can be a lot better' - what the managers said
Southampton manager Ralph Hasenhuttl, speaking to Match of the Day: "We started well but to be honest we are far away from our best, and against the best opponents you only have the chance to take something if you play your best.
"We were too slow in our minds, too slow on the ball. They showed us every weakness we had and we have a lot of them at the moment.
"When they build up from behind and score we must say 'OK', but to give the chances we did against such an opponent, you cannot handle it. That was the reason we were 3-1 down in the first half. Second half was a little better but not really, we never had the chance to come back.
"We know it is a tough situation, but we must work really hard and that's what we will do."
Chelsea manager Frank Lampard, speaking to Match of the Day: "Tammy's performance was great, his all-round performance and his work off the ball. But I must say, I thought Willian was immense - he was an example in what he was doing on and off the ball. He's a leader - not one that shouts - but in how he performs."
On Callum Hudson-Odoi: "I liked a lot of the stuff he did, there's competition in those wide areas now. I thought it was a really good performance, really bright stuff. I'm disappointed he didn't get his goal."
Southampton travel to Wolves in their first game after the international break on Saturday, 19 October (kick-off 15:00 BST), while Chelsea welcome Newcastle United to Stamford Bridge at the same time.
- 22RedmondSubstituted forBoufalat 81'minutes
- 9IngsSubstituted forAdamsat 81'minutes
- 7LongSubstituted forObafemiat 73'minutes
- 5JorginhoBooked at 12mins
- 19MountSubstituted forKovacicat 80'minutes
- 9AbrahamSubstituted forBatshuayiat 84'minutes
- 20Hudson-OdoiSubstituted forPulisicat 80'minutes
- Paul Tierney
- Shots on Target
Second Half ends, Southampton 1, Chelsea 4.
Corner, Chelsea. Conceded by Jan Bednarek.
Mateo Kovacic (Chelsea) wins a free kick in the defensive half.
Foul by Sofiane Boufal (Southampton).
Attempt missed. Che Adams (Southampton) with an attempt from the centre of the box misses to the right. Assisted by James Ward-Prowse with a cross following a set piece situation.
Foul by César Azpilicueta (Chelsea).
Sofiane Boufal (Southampton) wins a free kick on the left wing.
Goal! Southampton 1, Chelsea 4. Michy Batshuayi (Chelsea) left footed shot from the left side of the box to the bottom left corner. Assisted by Christian Pulisic with a through ball.
Foul by N'Golo Kanté (Chelsea).
Pierre-Emile Højbjerg (Southampton) wins a free kick in the defensive half.
Substitution, Chelsea. Michy Batshuayi replaces Tammy Abraham.
Foul by Christian Pulisic (Chelsea).
Yan Valery (Southampton) wins a free kick in the defensive half.
Substitution, Southampton. Che Adams replaces Danny Ings.
Substitution, Southampton. Sofiane Boufal replaces Nathan Redmond.
Foul by Tammy Abraham (Chelsea).
Jan Bednarek (Southampton) wins a free kick in the defensive half.
Substitution, Chelsea. Christian Pulisic replaces Callum Hudson-Odoi.
Substitution, Chelsea. Mateo Kovacic replaces Mason Mount.