SPAL have confirmed Mohamed Fares tore the anterior cruciate ligament in his left knee, so is expected to be out for several months.
The injury was more serious than previously anticipated and sustained when he changed direction during a friendly against Cesena on Thursday.
A statement from the club made clear the diagnosis of a torn ACL in the left knee.
The Algeria international will have surgery over the next few days.
This sort of injury generally requires four to six months out.