Cardinals quarterback Carson Palmer has been ruled out of Thursday night's game against the San Francisco 49ers after sustaining a concussion in last week's loss to the Los Angeles Rams, the team announced.
Palmer entered concussion protocol and underwent tests on Monday before it was announced that he would not travel to San Francisco.
Head coach Bruce Arians was optimistic that Palmer would be able to return in time for the following Monday Night Football contest against the New York Jets on Oct. 17.
Drew Stanton is expected to start in his absence. He threw two interceptions after taking over for Palmer against the Rams.
Palmer has thrown for 1,150 yards and six touchdowns on the season, leading the Cardinals to a 1–3 record.