8:42 AM ET

Sassuolo players celebrate their fifth goal in the win vs. AC Milan. MIGUEL MEDINA/AFP via Getty Images

AC Milan were humbled 5-2 at home by lowly Sassuolo in Serie A on Sunday, suffering a fourth defeat in five matches to pile pressure on manager Stefano Pioli.

Tempers flared throughout the match as Milan’s frustrations grew, with 11 yellow cards shown, seven to Milan players and four for the visitors.

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The Italian champions are fourth in the standings with 38 points, one ahead of Lazio and Roma, who play later on Sunday. Sassuolo are 16th.

Olivier Giroud thought he had given Milan the lead in the eighth minute, but his celebrations were cut short after being ruled offside by VAR.

Sassuolo’s first goal came against the run of play after 19 minutes when Domenico Berardi sent a cross into the box and an unmarked Gregoire Defrel tapped in.

Davide Frattesi doubled the lead two minutes later when he hammered a low shot into the net.

Giroud pulled one back for Milan in the 24th minute, heading Davide Calabria‘s cross into the top corner, but Berardi quickly restored Sassuolo’s two-goal lead.

Ante Rebic had a good chance to get a goal in first-half stoppage time, but Sassuolo keeper Andrea Consigli saved his volley.

Milan’s woes continued in the second half when Armand Lauriente converted a penalty two minutes after the interval, and Matheus Henrique added the fifth 11 minutes from time.

Milan had their second goal ruled offside by VAR in the 54th minute when a set piece found an unmarked Rebic inside the box, who tapped it in the net.

Divock Origi grabbed Milan’s second goal with a well-placed strike from the edge of the box in the 81st minute.