Update: The Dallas Cowboys fear that linebacker Sean Lee has a torn ACL, a source close to the organization told Joe Trahan.
Lee had to be helped to the training room early Tuesday afternoon during the first day of Cowboys organized team activties at Valley Ranch. His reaction indicated the injury was serious.
If the team's fear is realized and Lee does have a tear in his anterior cruciate ligament, he would need six to eight months to rehab, likely sidelining him for the entirety of the 2014-15 season.
The injury was caused when Lee engaged in a block with first round draft pick and offensive lineman Zack Martin.
Head coach Jason Garrett told the media that he doesn't know much about Lee's injury, but that it's a left knee injury and Lee was headed to the doctor.
Bryan Broaddus of dallascowboys.com originally reported that the injury appeared to be a hamstring or groin injury, not related to Lee's neck injury that sidelined him at the end of the 2013 season.
The Cowboys' star linebacker is yet to play a full season in his four years with Dallas since being drafted in the second round of the 2010 draft. Lee did miss three weeks with a hamstring injury earlier in the 2013. The severity of Lee's injury in OTAs Tuesday hasn't been reported, but, according to Trahan, Lee was very unhappy while being assisted off the field.