A team source said Claiborne had not passed the necessary tests for his concussion as of late Saturday. Barring a late and dramatic change, the first-round draft pick will miss his first game.
Claiborne felt dizzy Thursday, but said Friday that he was feeling good. Cowboys defensive coordinator Rob Ryan was more realistic.
"I know he's doing everything he can," Ryan said Friday. "He's got to pass these (concussion) tests. That's the one thing about it. You have to follow protocol and no one can rush it no matter who you are. I think it's great for the players' safety. You have to make sure when they do come back they are ready with no trouble coming back. When Mo comes back he'll be ready to go, but until then we'll just move forward."