Diogo Jota scored his first Premier League goal as Wolverhampton Wanderers came from behind to stun title hopefuls Chelsea 2-1 at Molineux on Wednesday.
Ruben Loftus-Cheek gave the visitors a halftime lead but two goals in four minutes from Raul Jimenez and Jota turned the match in favour of the hosts, who claimed their first win in two months.
Chelsea trail league leaders Manchester City by 10 points and host Pep Guardiola's side on Saturday, while Wolves climbed to 12th after ending their horror run of form.
"It was a good performance, even in the first half when we were behind," Wolves manager Nuno Espirito Santo said.
"They [Chelsea] have enormous quality and [Maurizio] Sarri's possession game is very hard to counter. But the boys did that and stayed in the game.
"The win was important, we have been showing this form for a long time. Playing Chelsea and coming from behind ... it is a great credit to the players, but you have to stay balanced."
Chelsea went ahead on 18 minutes when Loftus-Cheek scored for the second match in a row, his shot from outside the box deflected into the Wolves goal by the head of home captain Conor Coady.
The visitors had a strong call for a penalty turned down minutes after halftime when Alvaro Morata was clattered from behind as he seemed destined to score but it was the home side who found the back of the net on the hour-mark.
The impressive Morgan Gibbs-White fed Jimenez, who had a lot to do from a tight angle but drilled the ball past Chelsea keeper Kepa Arrizabalaga.
Four minutes later the home side were ahead when Matt Doherty provided a low cross that was tapped in at the back post by Jota.
"I think we played very well for 55 minutes," Chelsea manager Maurizio Sarri said.
"After the first goal, which was an accident because we were in full control of the match, we were suddenly a different team, I don't know why.
"I am really very worried, not about the result but for the fact we didn't respond to the first goal."
Sarri also refused to blame the penalty incident involving Morata on his side's defeat.
"I don't know about that, but we could have scored four or five goals and we missed them," he said.