Juventus, who have won only one of their last five games and have dropped 18 points from winning positions this season, stay on 80 points followed by Atalanta with 74 and Inter Milan on 73 with three games each to play.
Lazio clinch Champions League place with win over Cagliari; With three games left to play, Lazio still have a mathematical chance of overhauling leaders Juventus.
Juventus must wait to claim a ninth successive Serie A title after they slumped to a shock 2-1 defeat at lowly Udinese on Thursday after Seko Fofana scoring a stoppage-time winner with a solo goal.
Needing a victory to wrap up the title with three games to spare, Juve produced another strangely subdued performance but went ahead with a long-range shot by defender Matthijs de Ligt three minutes before halftime.
However, Ilija Nestorovski's diving header and Fofana's superb individual effort stunned the Turin side on a stifling evening.
Juventus, who have won only one of their last five games and have dropped 18 points from winning positions this season, stay on 80 points followed by Atalanta with 74 and Inter Milan on 73 with three games each to play.
Fourth-placed Lazio have 72 points after beating Cagliari on Thursday and now have three matches remaining. The win took Udinese up to 15th place on 39 points, seven points clear of the relegation zone.
It was the latest twist in an extraordinary title race which has seen three of the four contenders repeatedly drop points. Inter have won only two of their last six matches and Lazio had taken one point from a possible 15 before Thursday.
"We lost a bit of order," said Juve coach Maurizio Sarri.
"We lost in the 93rd minute because we were trying to win at any cost. This season is difficult, all the teams are playing in conditions different to the usual ones and everyone is tired."
Atalanta's next match is at AC Milan on Friday while Inter visit Genoa on Saturday and Juve host Sampdoria on Sunday.
Juventus had a lucky escape when Danilo headed Ken Sema's cross against the post while Udinese's Bram Nuytinck was also spared embarrassment when his back pass almost trickled into the net but goalkeeper Juan Musso pushed it wide just in time.
Musso also did well to turn away a Paulo Dybala shot and Cristiano Ronaldo was close from long range before Juve broke the deadlock three minutes before halftime.
A Udinese clearance landed at the feet of De Ligt and the Dutchman took one touch and drove a low shot into the net from 25 metres.
However, Udinese found a deserved equaliser seven minutes after the restart. Sema swung a cross over to the far post where Nestorovski met it with a diving header which flew into the net.
Udinese defended doggedly before snatching the winner on the break. Ivorian Fofana collected a loose ball on the halfway line, charged forward, nutmegged De Ligt and slotted his shot under Wojciech Szczesny to give his side a memorable win.
Later game on Thursday, Lazio claimed a Champions League place, ending a 13-year absence from the competition, when they came from behind to beat Cagliari 2-1 in Serie A on Thursday following five games without a win.
Serie A leading scorer Ciro Immobile netted the winner with his 31st goal of the season as Lazio, fourth with 72 points, clinched the final Italian place in Europe's elite club competition next season.
With three games left to play, Lazio still have a mathematical chance of overhauling leaders Juventus, who lost 2-1 at Udinese on Thursday and have 80 points.
"I'm happy, it's right to celebrate reaching an important target for us which we achieved three matches in advance," said Immobile.
"We are proud despite the difficulties we have faced after lockdown. This is something that Lazio haven't achieved for years."
Cagliari forward Joao Pedro scored with a stunning free kick early on but it was disallowed because the referee had signalled it was indirect.
Lazio were kept at bay by Cagliari goalkeeper Alessio Cragno and were caught out when Giovanni Simeone gave the Sardinians the lead with a deflected shot at the end of the first half.
However, Sergej Milinkovic-Savic volleyed Lazio level two minutes after the break and, after hitting the post with a shot on the turn, Immobile latched on to Luis Alberto's through ball to slot the winner past Cragno on the hour.
