OXNARD, Calif. -- With center Phil Costa out at least for the preseason opener with a back injury and the top two backups sidelined, the Dallas Cowboys will bring in former Philadelphia Eagles center Jamaal Jackson today, two sources said.
If Jackson is in shape, the Cowboys will sign him and hopefully have him at practice Wednesday.
Jackson played nine years for the Eagles, making 72 starts before being released after last season. He went to minicamp with the New York Giants in May on a tryout basis but quit afterward, saying his heart wasn't in it.
An MRI on Costa came back negative. Owner Jerry Jones said there were no disk issues and believes Costa will be back on the practice field this week.
"I don't see Costa out [this] week at all," Jones said. "The real question for me is, will we play him Monday?"
Jones said the Cowboys still need help at center with Bill Nagy (ankle) and Kevin Kowalski (ankle) out with injuries. Neither is expected back soon. Nagy will visit a foot and ankle specialist in North Carolina this week and will probably have to undergo surgery.
Second-year player David Arkin shifted from guard to center and will start against the Raiders. But he has struggled with the position switch and has had problems with shotgun snaps.
The rash of injuries that has marred the Cowboys' training camp claimed another victim Saturday when receiver Dez Bryant felt tightness in his hamstring and was taken out of drills.
Jerry Jones said he doesn't believe the injury is serious, but the team wasn't taking any chances on Bryant and may keep him out of Monday's preseason opener against the Raiders.
"This early in camp we are not going to push hamstrings," Jones said.
If Bryant doesn't play then the Cowboys will be without their top two receivers in the preseason opener. Miles Austin is already sidelined with a hamstring injury.
The injuries will give the Cowboys a chance to get an extended look at the young receivers battling for the No. 3 spot, including Kevin Ogletree, Dwayne Harris, Cole Beasley, Andre Holmes, Tim Benford and Raymond Radway.
Vice president Stephen Jones expressed anger Saturday over reports stemming from a Friday radio interview that he was frustrated with rookie cornerback Morris Claiborne over the sixth overall pick's inability to practice because of a knee sprain.
"I didn't rip Mo," Jones said Saturday. "It's wrong. There's no frustration at all. I have zero worries about Mo Claiborne. How that gets out there is beyond me."
Jones told KRLD/105.3 FM that Claiborne needs to be on the practice field more than he has thus far.
On Saturday, Jones said he was talking in general about the number of injured players and how they have to get back on the field.
Claiborne went through a walk-through Thursday and received limited reps in Saturday's workout. He will miss Monday's game.
Clarence E. Hill Jr., 817-390-7760