Gennaro Gattuso is facing six months on the sidelines after provisional tests revealed he has torn his anterior cruciate ligament in his knee.
The AC Milan enforcer showed no apparent signs of injury in Sunday's win over Catania, but severe pain after the match lead to the tests on Monday.
30 year old Gattuso was already suspended for this week's critical away clash at Juventus, but confirmation of the injury will rule him out for the rest of the season.