USC linebacker Lamar Dawson said it was "heartbreaking" to spend more than a year sidelined.
Dawson, 6-foot-1 and 230 pounds, suffered a torn anterior cruciate ligament during practice before the eighth game of the 2013 season and underwent knee surgery.
His recovery took longer than expected.
"It was just a period of time where I had to focus on myself and just get back to where I was in the past," the fifth-year senior said.
Dawson, a three-year starter, has stood out this spring during his first complete practices under second-year Coach Steve Sarkisian.
"[He is] a guy who continues to show up and do those things that we think he is capable of doing," Sarkisian said.
Dawson said the biggest adjustment returning to the field with a new staff was "just running the plays and just making sure I know my assignments."