Purdue senior linebacker Sean Robinson is out indefinitely after suffering a severe injury to his ACL, coach Darrell Hazell announced on Tuesday.
Robinson ranks third on the team with 42 tackles. Over 11 games (and nine starts) last season, Robinson recorded 45 tackles and two tackles for loss.
The Illinois win marked Purdue's first Big Ten victory under Hazell, who is in his second season as head coach. The Boilermakers finished 1-11 last season.
Purdue (3-3) hosts No. 8 Michigan State on Saturday.