DURHAM, N.C. -- As feared, Duke will not have All-ACC linebacker Kelby Brown this season after he suffered a torn ligament in his left knee during Monday's scrimmage.

An MRI exam Monday night revealed a torn anterior cruciate ligament in the injured knee. Brown will need surgery to repair the damage and is out for the season.

A redshirt senior from Charlotte, Brown missed the 2012 season after suffering a torn ACL in his right knee. He also tore the ACL and medial collateral ligament in the right knee in 2010.

NCAA rules allow players to use their four seasons of eligibility in five years. But should Brown wish to play his final season at Duke in 2015 the school could request a waiver to gain him a sixth year of eligibility.

Such waivers are almost always granted when an athlete misses two seasons due to catastrophic injuries. That was the case for Duke defensive end Kenny Anunike, who enrolled a Duke in 2008 and completed his career last season after sitting out two seasons with knee injuries Brown injured his left knee on the second play during Monday's scrimmage at Duke's Brooks Practice Facility.

Working with the first-team defense, Brown was rushing quarterback Anthony Boone when he crumpled the ground in the backfield. He emphatically pounded his fist on the ground and yelled "No!" before the medical staff came to his aid.

He was helped off the field, putting some weight on his left leg, and was treated on site before being carted off a few minutes later for further exams. Dr. Claude T. Moorman, the head physician for Duke's athletic teams, was on site at the scrimmage and aided in Brown's immediate treatment.

Brown recorded 114 tackles last season when Duke went 10-4 to win the ACC Coastal Division championship and finish No. 23 in the final Associated Press poll. Known for his knack for making big plays, Brown had 11 tackles for losses, one sack, two interceptions, two forced fumbles and two fumble recoveries.

Deion Williams replaced Brown with the first-team defense after the injury occurred on Monday. The Blue Devils have another option in redshirt senior linebacker C.J. France, who recorded two sacks in Monday's scrimmage while working with the second-team defense.