Rookie linebacker Sean Lee was injured on a second-quarter kickoff, and starting safety Gerald Sensabaugh went out later in the quarter. It's not clear how Sensabaugh, who already had an interception and a sack in the game, was hurt.
After the game, Sensabaugh said he couldn't remember his interception or sack.
"It's always disappointing when you can't play," Sensabaugh said. "I tried to go back out there but I guess I was a little discombobulated."
The Cowboys have a short week, which could prevent Lee or Sensabaugh from being ready to face Arizona on Saturday night.
Players who suffer concussions have to pass a series of tests before being allowed to return to action. Cornerback Orlando Scandrick needed four days to recover before he was able to get back to practice a few weeks ago after suffering a concussion.
"I feel good now," Lee said after the game. "I don't remember much. I looked at Keith Brooking after a series and asked him how I did and he goes, 'Uh, you didn't go back in.' But I'll be good."
Sensabaugh was optimistic that he'd be able to play on Christmas night.
"I've not had one in a long time," Sensabaugh said of the concussion, "but I should be OK."
Lee, a second-round pick in the 2010 draft, had been coming on strong in recent weeks but has been prone to injury.
He missed the 2008 season at Penn State because of a torn ACL in his right knee. Lee missed the Cowboys' rookie minicamp waiting for his knee brace to arrive, then missed time in training camp with a quad injury. Once the season started, he had hamstring and shoulder issues.