Dallas Cowboys middle linebacker Sean Lee reportedly has a torn ACL in his left knee and will likely miss the 2014 season.
Lee was hurt during the team's first organized team activity workout Tuesday, as he went down while being blocked by rookie guard Zack Martin. He was helped off the field by trainers.
The Cowboys have said only that Lee injured his left knee, but the Dallas Morning News cited sources as saying an MRI exam revealed the torn ACL.
Lee, the quarterback of the Cowboys' defense, had 99 tackles and four interceptions in 11 games last season. He missed five games because of injuries.
The Penn State product also missed 10 games in 2012 due to a toe injury, and hasn't played 16 games in a season yet.
"Sean has had to deal with injuries throughout college and also here in the NFL," said Cowboys coach Jason Garrett on Tuesday. "He really does everything he can to get himself ready to play. Unfortunately he had to deal with a few of those things, but he's as mentally tough as an individual as I've ever been around. Whatever the circumstances are he always puts his best foot forward and strives to be his best. I don't anticipate this being any different."
In 46 career games over four seasons with Dallas, Lee has 294 tackles and 11 interceptions.