Offensive line injuries piling up: No position has been bitten by the injury bug as badly as the offensive line, particularly in the middle. Veteran guard Mackenzy Bernadeau (hip) and second-year pro Kevin Kowalski (ankle) are both on PUP (Physically Unable to Perform) and unlikely to return anytime soon. Guard/center Bill Nagy is out for two to four weeks with a high-ankle sprain.

To make it worse, starting guard Nate Livings left Wednesday afternoon's practice with a hyper-extended knee. Livings will take advantage of the day off on Thursday. It’s likely he will miss a few days and possibly the intra-squad scrimmage scheduled for Sunday afternoon.

So that begs the question: Who is left at guard and center?

The Cowboys finished practice with David Arkin and Ron Leary on the first team. Harland Gunn, an undrafted rookie from Miami (Fla.), is the only backup and he’s taking some reps at center too.

Early day off for players: The Cowboys have yet to get into a smooth rhythm at camp, as they spent two days in California with conditioning before practicing for two days without pads, followed by one full-padded practice on Wednesday. And now the Cowboys have their first day off of camp with no meetings, practices or interviews for 24 hours until Thursday night’s meeting.

A group of injured players, including cornerback Mike Jenkins (shoulder), worked on their conditioning Thursday morning, 

Taking it slow with Ratliff: The Cowboys continue to be overly cautious with Pro Bowl defensive tackle Jay Ratliff, who is dealing with plantar fasciitis in his foot. The injury has slowed Ratliff all summer, but coach Jason Garrett said he’d rather be cautious now than to let it linger.

“That’s what we’re trying to avoid,” Garrett said. “We don’t want this thing becoming a major problem down the road. He’ll get plenty of rest. We’re just trying to work him back at a good pace.”

In the meantime, a healthy battle between Josh Brent and Robert Calloway is brewing. Brent gets more first-team reps with Ratliff out, but Calloway is making a strong push.

Position swap for two DBs: Even with just one full-padded practice, and only three total practices, the Cowboys already have swapped positions for two defensive backs.

Akwasi Owusu-Ansah, a fourth-round pick in 2010 who started out at safety and ended the year as a wide receiver on the practice squad, has been moved to cornerback, a spot he played briefly in college at tiny Indiana University of Pennsylvania. The depth hasn’t changed considering the Cowboys are now playing Mario Butler at safety. Butler spent last year on the practice squad at cornerback. The Cowboys are looking for better coverage in the slot, hoping Butler can bring some corner-like traits to the safety position.

For more Cowboys news and notes, follow Nick Eatman on Twitter @CBSSportsNFLDAL.