The junior went down with an apparent injury during 11on11 drills. He was tended to on the field by trainers before being helped off.
Interim head coach Ed Orgeron announced Wednesday that Dawson suffered a "severe" knee injury and will miss the final six games on the Trojans 2013 schedule.
In Dawson's absence, redshirt sophomore Anthony Sarao is now taking first team reps at linebacker.
Starting in all seven games this season, Dawson made 35 tackles, 3.5 for a loss and recorded 1.5 sacks.
Taylor Ross undergoes surgery
Just minutes after Dawson went down on Tuesday, walk-on tailback Taylor Ross followed.
The redshirt sophomore laid on the field for an extended period of time with trainers before medics were called. Ross was eventually put on a backboard and carted off the field to a waiting ambulance with an apparent knee injury.
"We have positive news on Taylor Ross," Orgeron said on Wednesday. "I spoke to his momma and I believe there was an operation that took place last night or this morning and he's in good shape and good spirits."
Orgeron also announced Wednesday that senior safety Gerald Bowman will redshirt the 2013 season. Bowman will undergo shoulder surgery.
Redshirt junior D.J. Morgan will also be out this season Orgeron announced Wednesday. He has yet to participate in practices or contests this year.