OXNARD, Calif. -- Cowboys center Phil Costa is getting an MRI today on his lower back. But he's not the only player dealing with an injury. Some updates:

*Guard/center Bill Nagy is headed to Charlotte to visit Dr. Bob Anderson, a foot and ankle specialist, next week to get his left ankle checked. Nagy has been out since the early stages of training camp with a high ankle sprain that's not getting better. Coach Jason Garrett said it's being determined if Nagy needs surgery; if that's the case, he could miss the 2012 season.

*Guard Mackenzy Bernadeau is getting work with the first- and second-team offenses and Garrett is hopeful he can play in Oakland on Monday night. The Cowboys have numerous issues at center given the health of Costa, but Garrett said Bernadeau will play guard and move to center in an emergency situation.

*Cornerback Teddy Williams and defensive end Marcus Spears, who have returned from concussions, will play at Oakland. Each has practiced without incident the last few days.

*Rookie wide receiver Danny Coale is still recovering from broken little toe and won't play at the Raiders. The team is being cautious with Coale, who should be ready to play at San Diego in the second preseason game.

*Rookie cornerback Morris Claiborne, as expected, won't play at Oakland. He's sprinting and doing some light things in walkthroughs but is not ready to practice in full pads yet.

*Nose tackle Jay Ratliff (foot) is getting limited snaps in full pads -- he picked up two on Friday -- but he's not ready to play yet. Ratliff could play at San Diego.

* LB Isaiah Greenhouse broke his right thumb and is in a cast. He will likely need surgery. The injury happened Thursday, but Greenhouse was unaware of the severity until X-rays were taken Friday.