Palmer was seen getting checked by Arizona's trainers on the sideline following the quarterback takedown, and then went to the locker room for his apparent injury. Drew Stanton came on to replace the veteran quarterback.
Arians also stated that the team will be "very, very careful" in dealing with Palmer's concussion, and said it will be tough for Palmer to play on a short week against the 49ers on Thursday night.
Before Palmer left the game, the Cardinals were clinging onto a 13-10 lead. After a Chase Keenum to Brian Quick touchdown with less than three minutes remaining to give the Rams the late advantage, Stanton was unable to lead the Cardinals to victory following two interceptions on his two drives in action. He ended up completing four of his 11 throws after coming off the bench.
Palmer was 23 of 36 through the air for 288 yards along with a touchdown toss and interception before the injury. Stanton, a 10-year veteran, threw four passes in mop-up duty two weeks ago for his only prior season action in Arizona's blowout win against the Buccaneers.