Emiliano Buendia blew the title race wide open with a 95th-minute winner as Aston Villa beat Premier League leaders Arsenal 2-1 at Villa Park.
The substitute won it with almost the final kick of an enthralling contest to inflict defeat on Mikel Arteta's side and move Villa above Manchester City into second - now just three points behind the Gunners after an astonishing run of nine wins in 10 games.
Matty Cash had put Villa on course for the victory in the first half but Leandro Trossard came off the bench to equalise early in the second and there were opportunities for Arsenal to lead - Emiliano Martinez saving sensationally from Martin Odegaard.
But it was Buendia who was the hero to spark wild scenes of celebration in front of the Holte End and give Manchester City the chance to move within two of Arsenal if they win their game in hand. Villa will be dreaming of the Premier League title themselves.
Arsenal had needed David Raya to save well from Ollie Watkins early on but Martinez was certainly busy at the other end too, Eberechi Eze also having a goal disallowed for offside. It was Eze switching off defensively that led to Cash's opening goal, however.
The Villa full-back was free to arrow the ball through Raya for the breakthrough. Arteta's response of bringing on Trossard and Viktor Gyokeres for Eze and Mikel Merino turned the tide quickly but it was a hard-fought contest that ebbed and flowed thereafter.
While it would be wrong to say either side settled for a point, Arteta did opt to withdraw his scorer in favour of Myles Lewis-Skelly in an attempt to tighten up and avoid a first defeat since August, while Martinez took considerable time over his 94th-minute goal-kick.
But Villa got the ball forward with bodies in the box, Arsenal were unable to clear their lines as the supporters in the Holte End sucked the ball goalwards, and Buendia's rare calmness amid the subsequent melee has changed the complexion of this season.
Arsenal manager Mikel Arteta speaking in the press conference:
"We are disappointed about how we lost the game. First of all, congratulations to Villa because they are a very good side and they are very good at what they do. I thought we were going to win the game.
"Today the result could have been different but the reality is that it is not. We were unbeaten in 18 games and now the table is close."
Arteta confirmed that Trossard could only play a limited number of minutes, forcing him into the late substitution. "The situation with Leo is that he could only play certain minutes, we decided to do it early, that is the reason why we had to change him."
The challenge now is to lift his team again. "Everything they have put in, the last two weeks, to lose that way emotionally is touching, you just feel everything put in is not worth it, but is worth it," Arteta explained. "It will make us a better team again."
Aston Villa manager Unai Emery speaking in the press conference:
"So proud of how we are responding and how we focus on each match, also in Europe. The players are the protagonists. I am so proud of their work.
"I felt in 90 minutes that we had momentum. After their goal, we had 10 or 15 minutes to recover our structure. Again, we then dominated. We were pushing.
"Villa Park is something which we must feel always, how the supporters push us. We got the last goal for everything and because we believed that we could win this match."
When it was put to Emery that Arteta had suggested Villa are title contenders, he replied: "I am not thinking of it. I know 38 matches is very difficult. We are not a contender. If we were in the day 35, perhaps we can speak differently."
