While backing the injured Andre Gurode, who returned to practice Saturday, Costa made a case for more playing time. He can play both guard positions and most likely will get a shot at starting as the left guard alongside left tackle Doug Free.
Jerry Jones said he expects to see Costa play now.
"I thought Costa took every advantage of his opportunity in terms of the snaps," Jones said. "He really played well and Costa is going to play a lot for the Cowboys. Now. I don't know how that works, boy I'm glad we got him and at this juncture. I don't know of anyone that's had a better preseason than he's had. I would put him right at the top from my perspective of preseason work and how impressed we've been with him."
The Cowboys have no plans of moving Gurode to guard. Instead another injury -- to Montrae Holland, who hurt his back -- has allowed Costa to move into a potential starting role.
Holland missed the preseason opener and probably will be out of the Week 2 game against the San Diego Chargers. Costa will start at left guard.
You could say maybe the Cowboys could release Holland, but there are two factors at play here: Holland, in the last year of his contract, just received a $500,000 roster bonus, and Costa has started one NFL game. So despite playing well, he's still somewhat experienced.
The move is more about what Holland hasn't been able to do on the offensive line. He did play well early in the 2010 season when Kyle Kosier was injured and Leonard Davis was benched. But Holland came in at a team-high 340 pounds this training camp.
"He really gave it everything he's got on every play," Jones said. "We've got a lot of confidence in him on what he does when he gets in the game. Your main concern is to make sure he's in the top physical shape he can be in. That's a bigger priority to me than it is whether or not he can play or not. He's answered the bell every time we've ever put him in a game."