Monahan, a redshirt junior, tore his right ACL in practice Thursday. He tore his left ACL last year in the seventh game against Georgia. In 2008, a shoulder injury ended Monahan's season in the fourth game against Ole Miss.

Sophomore running back Zac Stacy, who went down with a left knee injury one play after Monahan was hurt Thursday, has been diagnosed with a sprained MCL. Stacy will be out 2-4 weeks and has a chance to be ready for the Sept. 4 season opener against Northwestern if all goes well, Coach Robbie Caldwell said.