The Bianconeri had been unbeaten and were looking for a third straight win
Juventus missed the chance to go top of Serie A after they slumped to a 4-2 defeat at Sassuolo.
The Bianconeri had claimed 10 points from an unbeaten start, but came unstuck at the Mapei Stadium as Sassuolo battled to a second league win.
After Juve midfielder Adrien Rabiot had fired an early shot wide, Sassuolo took the lead in the 12th minute when Armand Lauriente’s dipping shot squirmed past Juve keeper Wojciech Szczesny.
The visitors, though, hit back to level within 10 minutes.
Federico Chiesa sent over a deep cross from the left towards the far post where Weston McKennie was sliding in and Sassuolo defender Matias Vina got the final touch as the ball dropped into the net.
Manuel Locatelli drilled a low shot just wide before at the other end, Szczesny made amends for his early error with a fine one-handed save from Ruan Tressoldi’s downward header.
The Polish keeper, though, could do little to prevent Domenico Berardi from putting Sassuolo back in front five minutes before half-time.
Matheus Henrique rolled the ball across the edge of the penalty area and Berardi curled a fine left-foot strike into the corner to mark his 300th Serie A appearance with a fine goal.
There were penalty appeals from the visitors when Federico Gatti’s cross struck Ruan Tressoldi on the arm, but the referee’s decision not to award a spot-kick was backed up following a VAR review.
Juve coach Massimiliano Allegri made two changes for the start of the second half as Nicolo Fagioli and Samuel Iling-Junior replaced Fabio Miretti and Filip Kostic.
England Under-21 international Iling-Junior looked to inject fresh life into the Juve attack, darting down the left before a deep cross dropped just past the far post.
Sassuolo remained a threat on the counter, and Berardi slid Lauriente into the penalty area, but his wild shot flew over.
At the other end, Dusan Vlahovic scuffed just wide of the far post before Juve eventually equalised again with 12 minutes left.
Iling-Junior flicked down a deep cross at the back post and Fagioli cushioned it into the path of Chiesa, whose deflected strike flew in.
However, Sassuolo were soon back in front in the 82nd minute. Lauriente’s fierce drive was punched out by Szczesny, and Andrea Pinamonti nodded in the rebound.
Sassuolo keeper Alessio Cragno kept out Chiesa’s angled shot at the near post before substitute Gregoire Defrel almost scored another for the hosts on the break when his effort cannoned back off the crossbar.
The fourth goal did arrive in bizarre fashion during stoppage time when Gatti, under pressure from Henrique, knocked the ball back into an empty net after receiving a quick free-kick from Szczesny, who was left stranded out near the corner flag.