TEMPE, Ariz. -- The Arizona Cardinals may not have to rely on rookie quarterback Logan Thomas after all, as backup quarterback Drew Stanton passed the concussion protocol on Friday, a source told ESPN.com.

Even though Stanton is cleared to play, there's no indication that he'll play Sunday against the Washington Redskins.

Although he's passed the NFL's concussion protocol, it's not clear if Drew Stanton will play Sunday for the Cardinals. AP Photo/Jack Dempsey

On Friday, Cardinals coach Bruce Arians said if Stanton was cleared to play, he'd be "in the mix." How much, however, is yet to be seen.

It's possible Stanton could be healthy and available, and still not play if Carson Palmer returns this week.

Arians does not expect to decide on a starting quarterback until about two hours before kickoff, a source told ESPN NFL Insider Adam Schefter. But Cardinals' sources believe Palmer is the favorite to get the nod.

Stanton was limited in all three days of practice, according to the team's injury report. He was cleared to throw Wednesday after being knocked out of Sunday's game against Denver in the third quarter with a concussion. He left the locker room that day wearing sunglasses.

Earlier this week, Stanton said Friday would entail him meeting with a team doctor, taking the ImPACT test and then seeing an independent neurologist.

Stanton is 2-1 this season in his first starts since 2010.