HALFTIME substitute Gregoire Defrel scored to give Sassuolo only its third-ever Serie A victory against Juventus in 21 matches with a 1-0 win on Sunday.
Defrel struck in the second half and Juventus also almost conceded an own-goal in a largely mediocre appearance from Massimiliano Allegri’s team.
Juventus hosts runaway league leader Napoli next weekend.
Roma hosted Udinese later Sunday looking to consolidate third place in Serie A.
Seventh-place Juventus had been making a push for the Europe spots despite a 15-point penalty for false accounting. It had won seven of its previous eight league matches before losing to Lazio last weekend.
Sassuolo had the better of a dull first half but neither side had a shot on target.
Mattia Perin was standing in for Wojciech Szczęsny after the Juventus goalkeeper took a knock to the chest and struggled to breathe during the midweek win over Sporting Lisbon in the Europa League.
And Perin pulled off a stunning save to keep out Defrel’s header from point-blank range 12 minutes after the break.
Juventus defender Federico Gatti came close to scoring an own-goal in the 62nd when he tried to head away a shot on goal but it came off the left post.
However, Sassuolo broke the deadlock two minutes later when Nicolò Fagioli tried to clear a corner but it came straight to Defrel, who did well to control the ball and place a swiveling shot into the bottom right corner.
Juventus poured forward in search of the equalizer and Sassuolo goalkeeper Andrea Consigli did brilliantly to scoop Adrien Rabiot’s header out from under the crossbar.
Lecce was held to a 1-1 draw by bottom club Sampdoria in a result that did neither side any favors.
Sampdoria’s January signing Jesé netted his first Serie A goal in the 75th minute to cancel out Assan Ceesay’s first-half opener in a largely dominant performance from Lecce.
Samp remained stuck to the bottom of the table, 10 points from safety, with Lecce five points above the relegation zone.
Salernitana was two points above Lecce after drawing 1-1 at midtable Torino.