The Serie A title race is far from over, Juventus coach Massimiliano Allegri said after a first-half opener by Chinese Super League target Nikola Kalinic paved the way for Fiorentina's 2-1 victory over the champion on Sunday.
Juventus traveled to Florence looking for its fifth straight win since a 3-1 loss at Genoa at the end of November.
But not for the first time this season, the Turin giant was exposed by a committed, battling performance by a host side.
Kalinic, the subject of a reported big-money move to Tianjin Quanjian, paved the way for a memorable win with a 37th-minute opener. Milan Badelj added Fiorentina's second and although Gonzalo Higuain halved the deficit in the 58th minute, Juve couldn't muster an equalizer.
Juve's fourth loss in 19 games leaves the champion just a single point ahead of Roma, although the five-time consecutive champion has a game in hand.
Napoli is four points off the pace in third with Lazio a point further back.
With Roma, Napoli, Lazio and Inter all winning their games, Juve is well aware a bid for a record sixth straight title could be littered with obstacles.
"This shows that the championship is far from finished," said Allegri, who saw midfield maestro Paulo Dybala spurn the chance to add to Higuain's 58th minute strike when he fired over the bar.
"Roma and Napoli are just behind us, so it could go right to the end. This loss should remind us all that whenever it comes to playing Juventus, opposition teams give it more than 100 percent."
Although Juve will be favored to take the points from its postponed match against Crotone on Feb 8, the champion's title rivals will be quietly celebrating.
Roma traveled to Udinese's Friuli stadium looking to make it three wins in a row and went in front in the 12th minute when Radja Nainggolan turned on Kevin Strootman's chip from deep in midfield to beat Orestis Karnezis with a right-footed volley from eight yards.
Luciano Spalletti's men should have doubled their lead when a penalty was awarded minutes later for handball in the area, but Edin Dzeko fired over the bar.
"It's a win that allows us to keep track with the teams below us that also won their games," Spalletti told Radio Rai.
Napoli is also biting at Juve's heels.
Its last league defeat came at Juventus, at the end of October, but at home to league struggler Pescara the Azzurri were kept scoreless until Lorenzo Tonelli, Marek Hamsik and Dries Mertens tallied in the second half.
Lazio remains fourth, five points behind Juventus, after Ciro Immobile's second-half penalty secured the points in a 2-1 win over Atalanta that saw the coaches of both teams, Simone Inzaghi and Gianpiero Gasperini, sent off for dissent after angry exchanges with the referee.