Stamford Bridge had become an anxious place by the time Thomas Tuchel readied his final change in the 83rd minute. The doubts were starting to build. Under pressure after those limp defeats to Manchester City and Juventus, Chelsea were looking frazzled after allowing this game to spiral out of control, and it was hard to see where a winner was coming from when Tuchel turned to one of England’s forgotten men, telling Ross Barkley to come on instead of Kai Havertz or Hakim Ziyech. At that stage, with Southampton’s 10 men clinging on for a point after James Ward-Prowse’s red card, nobody could have predicted what was to come. Nobody imagined that those dramatic final minutes would feature Barkley making an instant impact moments after replacing Ruben Loftus-Cheek or, even more improbably, Timo Werner finally getting the better of VAR by scoring the goal that lifted Chelsea into first place. Werner must have wondered when his luck would turn. The German has had 16 goals disallowed since joining Chelsea for £47m two summers ago – the latest one arrived shortly before half-time here – and his head could have dropped. Yet Werner has become a cult favourite with the Stamford Bridge faithful and nobody could begrudge him his moment when he restored Chelsea’s lead with six minutes left, converting César Azpilicueta’s cross after Barkley had opened Southampton up. The moral of the story: never give up. Chelsea kept plugging away and there was more to come after Werner’s first league goal since April, Ben Chilwell adding gloss to the scoreline when he atoned for his part in Southampton’s equaliser by making it 3-1. Chilwell’s goal left Southampton, who are a point above the bottom three, with nothing to show from a spirited display. They had threatened to snatch their first win of the season after levelling through Ward-Prowse’s penalty. “We played a brave game,” Ralph Hasenhüttl said. “The red card changed everything.” Hasenhüttl did not offer a view on Ward-Prowse’s dismissal for fouling Jorginho after 77 minutes. He was more disappointed that his side could not hold out. Southampton had Chelsea worried; Tuchel, never the calmest of characters, had even been booked after taking his protests too far after Werner’s disallowed goal. Tuchel was even more animated than usual. The German wanted aggression from the first whistle and he raced out of his technical area to rip into Chilwell early on, hammering the left wing-back for failing to read a pass from Callum Hudson-Odoi. Chelsea had to respond after some choked displays. Tuchel made five changes after the defeat to Juventus and his lineup pleasingly featured three academy products. Loftus-Cheek was impressive in midfield, Trevoh Chalobah dropped into the right side of the back three and there was finally a chance for Hudson-Odoi to impress on the left wing. Hudson-Odoi had a good battle with Tino Livramento, who left Chelsea in search of games in the summer, and he thought that he had an assist when his cross was headed in by Werner, only for VAR to find a foul on Kyle Walker-Peters by Azpilicueta. Tuchel was livid when he realised that his side had not doubled their lead, although the eruption felt over the top. Chelsea had been in control since going ahead in the ninth minute, Loftus-Cheek flicking on Chilwell’s corner for Chalobah to tap home at the far post. Southampton were fortunate not to fall further behind. Chilwell, making his first start in the league this season, was thwarted by Alex McCarthy. Antonio Rüdiger later released Romelu Lukaku, who was denied his first goal in five games by a tight offside call. Yet there were flickers from Southampton. Adam Armstrong saw a deflected shot saved by Édouard Mendy, Theo Walcott headed wide and the visitors improved after half-time, the introduction of Ibrahima Diallo giving them more solidity in midfield. Chelsea dropped back and Livramento, showing why he was so highly rated at Cobham, won a penalty when his driving run drew a rusty challenge from Chilwell. Martin Atkinson pointed to the spot and Ward-Prowse drew Southampton level, calmly sending Mendy the wrong way. Now it was a proper contest. Mason Mount came on, increasing the tempo for Chelsea. Chilwell and Werner both went close and there was another twist when Ward-Prowse brought his studs down on Jorginho’s ankle. Atkinson checked the pitchside monitor and dismissed Southampton’s captain. Southampton’s momentum drained away. Tuchel replaced Mateo Kovacic with Jorginho and there were a few raised eyebrows when he introduced Barkley. Yet the changes worked. Barkley, whose Chelsea career looked over after a disappointing loan spell at Aston Villa last season, immediately lifted a glorious pass over to the right for Azpilicueta, who crossed for Werner to score from six yards. Southampton were beaten. Five minutes later a goalmouth scramble involving near misses from Lukaku and Azpilicueta ended with Chilwell’s rising shot just creeping over the line before McCarthy clawed it out. Chelsea’s redemption was complete.