University of Alabama outside linebacker Terrell Lewis suffered a torn ACL, according to a statement from the university.

“Terrell Lewis suffered a torn right ACL last week while training,” head coach Nick Saban said in a statement. “He underwent successful surgery today, and a timeframe for his return is unknown at this time.”

Lewis missed 10 games last season with an arm injury, but he returned for the Auburn game and the College Football Playoff. He recorded seven total tackles including a sack in the National Championship Game against Georgia in January.

Alabama lost another linebacker Monday when VanDarius Cowan was dismissed from the program for violating team rules.