Timo Werner looked to have done the damage to his former boss with his first Premier League goals and an assist for Kai Havertz to do the same before Jan Vestergaard headed past Kepa Arrizabalaga from close range two minutes into added time.

Werner’s 13-minute brace was rich reward for an electric attacking performance in the first half, spoiled just before the break when Danny Ings was slipped in to round Kepa and make it 2-1. The Saints restarted brightly and levelled through Che Adams but Havertz’s quickfire goal restored our lead instantly.

As we held on in the dying minutes, the points were snatched from us in heartbreaking fashion when Vestergaard headed in Theo Walcott’s drive from the edge of the box.

Living up to expectations

Chelsea’s starting team looked like one that had goals in it, with the attacking triumvirate of Christian Pulisic, Mason Mount and Havertz starting together for the first time in support of Werner, who returned to a centre-forward role.

And so it proved with a lively start under a slate-grey London sky. Prior to the game, just one of our 10 Premier League goals this season had come in the first half, highlighting the need for Frank Lampard’s men to find a way to open proceedings with energy and on the front foot.

Ben Chilwell almost opened the scoring inside three minutes, forcing a good save down low from Alex McCarthy after neat interplay between Pulisic and Werner, before the visiting goalkeeper quickly jumped up to deny Havertz on the follow-up.

Pulisic had a chance in the air from Chilwell’s deep cross but miscued his header, while some excellent approach play on the left involving the full-back, Havertz, Mount and Werner saw the German escape into space but miss a team-mate with his low ball across the face of goal. In between, Kepa made a smart save to deny Adams inside the area.

Timo’s time

Werner thought he had opened his Premier League account a minute before he actually did, stooping to head Chilwell’s delivery past McCarthy before turning to see an offside flag chalk it off. However, the striker didn’t have to wait long to get himself off the mark.

The ball travelled patiently from right to left across the back four and then Chilwell punched it forward into the feet of Werner, whose clever dummy allowed him to escape Jan Bednarek and spin into the space behind the Saints centre-back.

There was still an awful lot to do but our number 11 did it with superb awareness, strength and finesse, carrying the ball onto his right foot before drilling it low into the back of the net for the opener.

Friends reunited

Ralph Hasenhuttl, the Southampton manager, ought to have been more aware than most of Werner’s attributes, having signed him when in charge of RB Leipzig and worked closely with him for two successful seasons there. Yet the 24-year-old continued to pose major problems to the visitors and soon doubled our lead with his second of the afternoon.

Moments before, lovely footwork in the six-yard box from Mount fashioned an opening, with Pulisic taking over and almost finding Werner with a cutback cut out by Vestergaard. The second goal came on 28 minutes and will have reminded Chelsea fans of one scored away at Watford last season, with Jorginho the architect as he played a brilliant first-time ball over the top of the Saints defence.

When you have the pace of Werner, you don’t need to be hanging on the shoulder of the last defender and the striker wasn’t but soon found himself ahead in the race for the ball, positioning his body cleverly in front of Bednarek as the pass dropped out of the sky.

If that was clever, the rest was class – a nonchalant flick over the onrushing McCarthy and a gentle nod into the unguarded net. Turbo Timo had the Blues racing into a two-goal lead before half hour had been played!

Saints steal a march before half-time

Lampard’s men were cruising, the front four combining brilliantly and looking likely to score every time they ventured forward, while the team’s counter-pressing when possession was lost was particularly impressive and influential in suffocating Southampton.

Kurt Zouma has started the season in prolific goalscoring form for a centre-back, having netted at Brighton and last time out against Crystal Palace, and the Frenchman would have had a third of the campaign were it not for the agile reflexes of McCarthy, who pushed away the defender’s powerful header from Chilwell’s inswinging corner.

It looked like being a case of when, not if, Chelsea would add a third to their tally but the Premier League so often has the habit of luring you into a false sense of security and Southampton stung the hosts two minutes before the interval.

Havertz was guilty of losing the ball to Adams in a dangerous area and the forward found his strike partner Ings with a swift pass forward that split centre-backs Christensen and Zouma. The England striker, who netted 22 league goals last term, was the last man we wanted to gift an opportunity to and he never looked like letting us off the hook as he rounded Kepa and turned the ball in to halve the deficit.

Changed contest

The visitors made every minute of their half-time break count, emerging almost five minutes late for the restart due to the long walk to and from their makeshift changing facilities. They looked a renewed team, buoyed with confidence following their goal and pushing for another against a Blues side slightly shaken.

Ings was proving their livewire and fired a warning shot narrowly wide from 20 yards, though the goal that restored parity for Hasenhuttl’s men was one of our own making as well. Zouma’s pass back to Kepa lacked the requisite power to reach its target, the goalkeeper slipped as he got there before Adams, Christensen slid in to block the ball on the line but Adams latched on to the loose ball and smashed it into the roof of the net for 2-2.

Finisher turns provider

No sooner had the Blues seen their two-goal advantage evaporate than the hosts conjured the game’s fifth goal. It was an attack down the right that did the damage, Werner and Pulisic combining well before the striker peeled away into space down the channel and then slid the ball perfectly into the middle for Havertz to steer in from close range.

Just like his countryman and provider, it was the 21-year-old’s first goal in the Premier League, adding to his Carabao Cup hat-trick here against Barnsley, but plenty of work still remained for Lampard’s men to see this game out.

Chances and late drama

Havertz’s technical skills are often what sets him apart but his impressive frame also makes him an aerial threat, particularly when latching on to Chilwell’s teasing deliveries. It was this combination that created a chance for the German with 14 minutes remaining as a corner was swung in from the left but his header was too high to trouble McCarthy.

Southampton intensified the pressure as the conclusion neared, with our one-goal lead a delicate one. Adams missed the target by less than a yard with a fierce strike across the face of Kepa’s goal before our Spanish stopper got down well to keep out an effort from Ings at his near post.

That looked to have kept the win safe but the visitors made it 3-3 right at the death when Walcott latched on to Bertrand’s cleared free-kick, fired the ball into the ground and through the box, where Vestergaard flicked it on its way into the bottom corner.

The selection

Pulisic started for the first time since the FA Cup final in one of four changes from our victory over Crystal Palace last time out. Kepa returned in goal, while Christensen and Mount were the others to come back into the side.

That meant Werner led the line up front, supported by an exciting attacking trio of Havertz, Pulisic and Mount in front of N’Golo Kante and Jorginho, who netted twice from the penalty spot in our last Stamford Bridge action.

Christensen replaced Thiago Silva at the heart of the back four, the Brazilian not considered for selection following a long cross-Atlantic trip on international duty, while Ben Chilwell was deemed fit enough to start again.

The Saints went with 4-4-2 in a sign that this could be an attacking afternoon in south-west London, with Ings and Adams up top. Former Blues Bertrand and Oriol Romeu started on their returns to Stamford Bridge, while Walcott made his second Southampton debut 15 years after his first.

What’s next?

The Champions League is back in three days as Sevilla visit the Bridge for our opening Group E fixture on Tuesday night, before a weekend trip to Manchester United. This Saints encounter was the first of seven games in three weeks for the Blues as a busy period begins in earnest.

Chelsea (4-2-3-1) Kepa; Azpilicueta (c), Christensen, Zouma, Chilwell; Kante, Jorginho; Mount (Ziyech 72), Havertz, Pulisic (James 87); Werner (Abraham 90)Unused subs Caballero, Tomori, Hudson-Odoi, GiroudScorers Werner 15, 28; Havertz 59Booked Chilwell 49

Southampton (4-4-2) McCarthy; Walker-Peters, Vestergaard, Bednarek, Bertrand; Walcott, Ward-Prowse (c), Romeu (Diallo 87), Redmond (Tella 77); Adams (Long 87), IngsUnused subs Forster, Stephens, Valery, ObafemiScorers Ings 43; Adams 57; Vestergaard 90+2Booked Romeu 84

Referee Peter Bankes