Second-placed Napoli threw the Serie A title race open in dramatic style on when Kalidou Koulibaly scored with a towering header in the last minute to give them a 1-0 win at leaders Juventus.
Napoli cut the gap between themselves and the Turin side to one point on Sunday with four matches to play, setting up a dramatic finale to the Italian top-flight season.
Napoli dominated the match but seemed to have run out of ideas and energy until the final minute when Jose Callejon's outswinging corner was met by the Senegal international with a monstrous header which left Gianluigi Buffon helpless.
"We have always believed in the title, we have to continue like this and believe in ourselves until the end," Koulibaly said.
It was Juve's first league defeat at home since a 2-1 loss to Lazio in October. Their last Serie A defeat in Turin before that was in August 2015.
"Winning here was practically mission impossible, we can be happy because we have played against a great team which hasn't lost at home for so long," Koulibaly said.
Juventus, chasing a seventh successive title, still face difficult matches away to Inter Milan and AS Roma.
"We mustn't make calculations, they're useless," Juventus coach Massimiliano Allegri said. "We just have to put this defeat behind us and prepare for the match in Milan.
"It's true that Napoli are favourites because of the fixture list but matches have to be won. I have seen a lot in football ... anything can happen."
Earlier Lazio thrashed Sampdoria 4-0, with Ciro Immobile scoring a brace to pile the pressure on third-placed Roma.
Lazio midfielder Sergej Milinkovic-Savic opened the scoring on 32 minutes before Stefan De Vrij netted the second 11 minutes later.
With five minutes to go, Ciro Immobile scored the third goal and added a fourth two minutes before the end of the game to drive home the win.
Lazio now have 67 points and hold fourth place on goal difference behind Roma, while Sampdoria remain ninth.
Elsewhere, Inter Milan earned a 2-1 away win over Chievo as they continued their push for a top-four spot.
Atalanta jumped to sixth place with 55 points after beating 10th-placed Torino 2-1.
Also on Sunday, Cagliari were held to a goalless draw against Bologna, while Crotone pulled off a 2-1 win against Udinese.
Defending champions Juventus lead the Serie A table with 85 points, four points above second-placed Napoli just hours before they face off on Sunday evening.