Updated with Lee having a left knee injury; MRI scheduled for late afternoon; RGIII tweet

The Dallas Cowboys have gotten used to linebacker Sean Lee being injured, but this is a little ridiculous. And, because of his history, the team is especially concerned about the left knee injury he suffered Tuesday.

Lee was hurt on the first day of Dallas’ organized team activities, slipping as he prepared to be blocked by offensive lineman Zack Martin, the player the team drafted instead of Johnny Manziel. “I know he was chasing a play out to the side, and he went down,” Coach Jason Garrett said (via ESPN Dallas). Garrett added that Lee would undergo an MRI at 6 p.m. EDT.

Lee missed five games last year because of a quadriceps injury and 10 in 2012 because of a broken toe. Robert Griffin III put aside the Cowboys’ rivalry with the Washington Redskins to wish Lee well.

“Unfortunately, he’s had to deal with a few of these things,” Garrett said. “But he’s as mentally tough an individual as I’ve ever been around, so whatever the circumstances are, he always puts his best foot forward and strives to be his best. So don’t anticipate this being any different.”

Lee was helped off the field by two trainers and muttered a profanity as he was taken into the locker room.

Video shot by Calvin Watkins of ESPN Dallas shows Lee being helped off the field.