Barber, who led the team with 932 rushing yards, suffered the injury in a Week 2 loss against the New York Giants at Cowboys Stadium.
Cowboys running back coach Skip Peete said it's a six-week injury. Barber missed just one game.
"He still has a hole in it," Peete said Tuesday.
Barber, who doesn't speak to reporters, battled numerous injuries last season. In addition to the quad injury, Barber played with a bruised left knee and a broken thumb. In the two playoff games, Barber battled thigh and knee issues, and rushed for just 18 yards on 11 carries with no touchdowns.
But the quad injury, originally described by team officials as a bruised thigh, earned him plenty of respect in the locker room.
"That just shows you how strong-willed he is," fellow running back Felix Jones said. "He's one of the more physical guys in the world. It's like a slap in the face to criticize him. You're putting your body on the line in getting hit from all types of directions. That's somebody you look up to. He's shown us a lot."
In the offseason, Barber has worked hard to take 10 pounds off his 6-foot, 222-pound frame to add quickness so he can become more elusive. In the last two years, former Cowboys running backs Emmitt Smith and Tony Dorsett have noted that Barber needs to avoid hits so he can have a longer career.
Barber has not rushed for more than 1,000 yards in a season during his career, yet he remains the Cowboys' starting running back. Cowboys owner/general manager Jerry Jones said he wants his lead back to become more of a closer, especially when the Cowboys are trying to close out ballgames.
"There is no question about his toughness," Cowboys strength and conditioning coach Joe Juraszek said. "He's prideful about his job. As tough as he is and as much pride as he is, for him to miss any time is a surprise to me."