OXNARD, Calif. -- The Dallas Cowboys lost backup defensive end Tyrone Crawford to a season-ending torn Achilles on the opening day of training camp Sunday, according to a team source.

"This is part of our game, and it's disappointing," Cowboys executive vice president Stephen Jones said before ESPNDallas.com learned the severity of the injury. "Crawford is probably our top young defensive lineman. That's a shame. Knowing him, he's such a diligent worker, he'll get right on it and be back."

Crawford, a 2012 third-round pick out of Boise State who was getting second-team snaps Sunday, banged his fist to the ground while receiving medical attention after suffering the injury. He was carted off the field with his head down, covering his face as fans encouraged him.