ARLINGTON, Texas -- Quarterback Jon Kitna missed Tuesday's walkthrough session with a sore lower back, and his status for the afternoon practice is uncertain.

"He didn't practice [Monday]. He hurt his back a little bit so we're just monitoring him day-to-day," coach Jason Garrett said. "We don't think it's a serious thing. Again like with some of the injuries we've had with some of our guys, it's a good opportunity for some of our younger players to get some more snaps. Stephen [McGee] got some more [Monday], Tom Brandstater got some more. We'll see how Kitna feels [later] today."

Second-round pick Bruce Carter, who has yet to practice this summer as he still recovers from a surgery on his ACL, said he will miss two more weeks.

Carter suffered the knee injury last December while playing for North Carolina. He received a letter from famed orthopedic surgeon James Andrews in the spring clearing him for football drills. The Cowboys have been cautious with Carter, an inside linebacker who saw his stock drop into the second round because of the injury.

"I try to use the time that I am out to try and learn the plays," Carter said. "And learn as much as possible so when I do get in I will be ready to go."

Carter currently is on the non-football injury list, and he might miss the rest of the preseason. If that happens, Carter would be moved from the NFI to the physical unable to perform list once the regular season starts.

Outside linebacker Brandon Williams (back) returned to practice after missing Monday's sessions.