Timo Werner ended his wait for a first Premier League goal of the season to help Chelsea defeat 10-man Southampton 3-1 and move the European champions top of the table on Saturday.
Chelsea, entering the game following successive 1-0 defeats to Manchester City and Juventus, got off to a fast start at Stamford Bridge when defender Trevoh Chalobah nodded home from Ruben Loftus-Cheek's flicked header in ninth minute.
The Blues continued to dominate much of the first half but were unable to capitalise on their advantage as Werner had a goal controversially ruled out by VAR shortly before the break when Cesar Azpilicueta was judged to have fouled Kyle Walker-Peters in the build-up.
The decision enraged Chelsea manager Thomas Tuchel, who was shown a yellow card by referee Martin Atkinson.
“I was very angry because I could never believe this could happen in the Premier League where you would go back to a 50/50 that wasn't even in close connection to the goal,” Tuchel said when asked about the incident.
Coming back out after the interval, Southampton manager Ralph Hasenhuttl introduced Ibrahima Diallo for Theo Walcott and moved to five at the back. The change in system appeared to work as the visitors started to impose themselves on the game.
Southampton pulled level in the 61st-minute when James Ward-Prowse slammed home a penalty following Ben Chilwell's rash challenge on Tino Livramento, who left Chelsea for Saints in the summer.
However, England midfielder Ward-Prowse went from hero to villain just 16 minutes later when his crunching challenge on Jorginho was upgraded from yellow to red following a VAR consultation.
It proved a pivotal turning point as Chelsea poured forward in search of victory.
Yet despite the domination, the hosts had to until late in the game to restore their lead having seen Southampton goalkeeper Alex McCarthy produce a stunning save to deny Werner.
There was no denying Werner in the 84th-minute, though, as the German forward poked home from captain Cesar Azpilicueta's skilful first-time cross. It was Werner's first Premier League goal since April.
Chilwell then atoned for giving away the earlier penalty when the England full-back scored a thunderous volley, which needed goal-line technology to confirm it had crossed the line after McCarthy looked to have produced another spectacular save. In the build-up to Chilwell's goal, Chelsea twice had chances to score only for Azpilicueta and then Lukaku to strike the bar.
The result moves Chelsea top of the table on 16 points, two before Liverpool and three clear of Manchester City, either of whom can move to the summit with victory when they face each other at Anfield on Sunday.
“For today we are top of the league and tomorrow there are still games,” Tuchel said. “After two defeats we had to be careful that we didn't start being too sad or too worried because there was a chance to be on 16 points.
“It was important to have a better performance than the last two games. We sharpened our mindset so that we are not afraid to lose. It was nice to play the way we did and get a deserved win.”
Southampton, meanwhile, sit 17th on four points and are still searching for their first win of the season.