The Italy U21 international could miss the remainder of the season after he was stretchered off during the 3-1 win.
"The first impressions of the medical staff are that the cruciate ligament has been broken, but we hope that is not the case.
"We are so happy for the win and the performance, but very sad about this terrible injury."
It was an ill-tempered match that saw Marcelo Zalayeta and Felice Piccolo sent off at half-time for a scuffle on their way down the players' tunnel.
"I told the referee he made the right decision. Zalayeta elbowed Piccolo and he reacted, so it is only right that both should be dismissed."