Juventus suffered a blow to their Serie A title hopes when Sergio Pellissier completed a hat-trick with a stoppage-time equaliser to give Chievo a 3-3 draw in Turin on Sunday.
Inter Milan, on course for a fourth successive scudetto with nine games left, can extend their lead over second-placed Juve to nine points with victory at Udinese later.
Striker Pellissier crowned a stunning display by heading in at the far post to stun Juve, who had come from behind twice before taking the lead.
"Today is a splendid day which I'll remember for a long time," Pellissier said.
Chievo have steadily moved away from the relegation zone in the last month and they soon showed Juve they were in no mood to end their good run.
Pellissier put Chievo ahead midway through the first half when he took advantage of Giorgio Chiellini's mistake to round Gianluigi Buffon and score.
Defender Chiellini, wearing a mask to protect a broken nose, made up for his error by smashing the ball in off the bar but Pellissier grabbed his second just before the break when this time he outpaced Olof Mellberg.
Chievo defenders Santiago Morero and Mario Yepes both touched the ball for an unfortunate own goal early in the second period and Juve went ahead with 11 minutes left when Vincenzo Iaquinta headed in Mauro Camoranesi's cross.
Pellissier was not to be denied however and Chievo deserved their draw against a lethargic Juve, who substituted the ineffective Alessandro Del Piero at halftime.
In other matches, substitute Thiago Motta netted in the second half to keep Genoa two points clear in fourth spot with a 1-0 win at almost doomed bottom side Reggina.
Fiorentina, in fifth, needed Alberto Gilardino's late goal to win 2-1 at Atalanta while sixth-placed AS Roma are three further back after two contentious penalties from Francesco Totti sealed a 2-1 home win over fourth-bottom Bologna.
Torino remain two behind Bologna after losing 1-0 at Palermo while second-bottom Lecce visit AC Milan in third later.