Nate Livings underwent knee surgery Friday morning, potentially leaving the Cowboys without their starting left guard from last year for much of the preseason.
The surgery was complete by the time the Cowboys started walk-through, said executive vice president Stephen Jones. The recovery is expected to be at least two weeks. The Cowboys begin their preseason schedule on Sunday night against Miami in Canton, Ohio, and play Oakland five days later.
The Cowboys are also missing last year's starting right guard, Mackenzy Bernadeau, because of a hamstring. But he was working in walk-through Friday for the first time in camp.
The Cowboys have been hampered by offensive line injuries in camp. Guard Ronald Leary returned to practice this week after missing the first week because of a calf strain. Backup tackle Jermey Parnell has missed all of camp with a hamstring injury, and reserve guard Kevin Kowalski was hurt in practice this week.
The Cowboys signed guard Jeff Olson and tackle James Nelson this week to help with training camp practices and the games.
-- Carlos Mendez