Carson Palmer unlikely to play Thursday after exiting Rams' game with concussion

Arizona Cardinals quarterback Carson Palmer left the team's game against the Los Angeles Rams on Sunday with a potential concussion. He exited the game in the fourth quarter and was quickly taken to the locker room to be evaluated as part of the league's concussion protocol. After the game, head coach Bruce Arians confirmed that Palmer has entered the league's concussion protocol, which puts his status for Thursday's game against the San Francisco 49ers in doubt.

Arians told reporters after the Cardinals' loss to the Rams that Palmer had been diagnosed with a concussion and the team will be "very, very careful" with him, according to NFL Network's Ian Rapoport.

Shortly after, the Cardinals announced that Palmer's return to the game was questionable while he undergoes evaluation. If they determine he sustained a concussion, he will not be able to return to the game.

At the time of injury, Palmer had completed 23 of 36 passes for 288 yards with a touchdown and an interception. The Cardinals trailed the Rams, 17-13, when Palmer exited the game.

Drew Stanton is the primary backup and entered the game after Palmer's injury.

Palmer has been the big reason the Cardinals have been a decent team the past couple seasons, but he has struggled big time this year. The 36-year-old entered Week 4 with just 862 passing yards, five touchdowns and four interceptions through three contests.