Kevin-Prince Boateng suffered racist abuse before AC Milan's 1-0 defeat at Juventus on Sunday, three months after being targeted by Pro Patria fans during a friendly game.
Boateng and the rest of his Milan team-mates walked off the pitch in January when a section of the Pro Patria support continually made monkey noises at him. He reacted to the Juve fans by putting a finger to his mouth to silence them.
Juve's stadium announcer had to intervene and plead with the fans to cease the abuse, and the club could yet face action from the Italian FA over the incident.
Juventus fans did display a banner which read: "No to racism; yes to jumping". This was in response to a previous banner shown by the clubs fans which read: "If you jump, [Mario] Balotelli dies".
Meanwhile, Milan coach Massimiliano Allegri does not fear the threat from Fiorentina as they bid to finish third and qualify for the Champions League. The defeat to Juve, coupled with Fiorentina's 4-3 home win over Torino, left Milan with just a one-point cushion in third.
"We are not worried," Allegri told Sky Sport Italia. "We have lost our first game of the year. Now we must try to do well in the next games to hold onto third place.
"We know that Fiorentina are a good side. We threw away a match point by not winning in Florence despite being 2-0 up. Now our calendar becomes easier. I am confident.
"It was an evenly balanced game in which we conceded very little to Juve. It was a game that seemed destined to end in a draw, but then we were punished for our only error in defence. Unfortunately we have also lost two players to injury and even [Riccardo] Montolivo was not at his best, physically."
Top scorer Stephan El Shaarawy had another off day, but Allegri insists he has full confidence in the forward to rediscover his form in the final five games of the Serie A season.
"He's a boy of 20 that has done very well up until now, but it's normal that there can be a dip [in form]," he said. "Physically, he's fine, but he must understand these difficult moments can happen."