Jannik Vestergaard's last-gasp leveller stole two-goal Timo Werner's thunder as Southampton battled to a 3-3 Premier League draw at Chelsea.
Defender Vestergaard rifled home in second-half stoppage time as Saints punished Chelsea's lax defending, with the recalled Kepa Arrizabalaga enduring another day to forget.
Werner thought he had won the day by shifting his Chelsea career into top gear, vindicating his £53 million ($68.4m) transfer fee to open his Premier League account in style.
Chelsea were cruising at 2-0 after Werner's brace – the first courtesy of a sublime dummy which bamboozled Jan Bednarek before firing home, and the second as he lobbed the ball over goalkeeper Alex McCarthy and nodded home.
But defensive frailties surfaced again for Chelsea as Danny Ings, who rounded Kepa before scoring, and Che Adams exploited glaring errors to draw Saints level at Stamford Bridge.
Kai Havertz then converted Werner's smart tee-up to put Chelsea back in front, but Chelsea could not hold on and defender Vestergaard forced in the late equaliser.
The out-of-form Kepa's latest clanger proved costly, with the Spain stopper colliding with the post when Adams scored his goal to make it 2-2 – and that after finding himself stranded from Kurt Zouma's shy back-pass.
Kepa's shot at redemption only came about so soon due to Edouard Mendy's thigh injury, and the 26-year-old will doubtless rue another missed opportunity to reassert his Stamford Bridge status.
The aggrieved Blues at least vented their clear frustrations in a quick-fire move to regain the lead.
This time Werner turned provider, laying the Blues' third on a platter for Havertz, who dinked home neatly.
Saints refused to let Chelsea coast to the win, with Adams firing wide after smart approach play from Theo Walcott, who impressed on his first Saints appearance in almost 15 years.
Kepa produced a good save to deny Ings, but Chelsea could not find the fortitude to hold on.
After a half-cleared free-kick, up popped Vestergaard with a low drive, that eluded everyone – to floor Chelsea and send Saints into wild celebrations.
For Werner, it proved to be a frustrating afternoon, despite his two goals. "I am happy about the goals but I want to win the game. 50 per cent I am happy, 50 per cent not," he said.
"I don't know if we have a problem but the last three games we concede six goals and it is not where we want to be, to compete for titles.
"In Germany we always say defence wins titles. If we concede so many it is hard to win games and win titles."
