Butler went down with just under 9 minutes to go in the Mountaineers' 78-57 loss as he drove the baseline and squared up to shoot. His left knee gave out and he immediately collapsed in pain, writhing on the floor as West Virginia Coach Bob Huggins consoled him.
Teammates eventually helped Butler to a cart and he was taken to the locker room for evaluation. School officials said Sunday he had sustained a torn anterior cruciate ligament.
Butler had 10 points at the time of his departure, his last game as a Mountaineer.