The rookie was injured after being hit high by defensive end Cliff Avril during practice Monday. He was carted off the team's practice field after being attended to by team trainers.
Schwartz says "he'll be back, but it won't be this season."
The Lions were counting on the second-round pick from Illinois to provide power in the backfield to go along with the speedy Jahvid Best.
The injury is just the latest for Detroit. The Lions' starting offensive tackles and a key backup are recovering from injuries.