Tempe, AZ - Arizona Cardinals coach Bruce Arians confirmed Monday that quarterback Carson Palmer tore the anterior cruciate ligament in his left knee and will be placed on injured reserve.

Palmer, 34, suffered the injury when he was sacked by Rams safety Mark Barron early in the fourth quarter of Arizona's 31-14 win over St. Louis on Sunday.

"It's just a shame it happened now, with this team," said Arians.

Palmer remained on the ground in obvious pain before limping off the field. He was then carted back to the locker room. Drew Stanton threw a late touchdown pass in relief of Palmer, helping the Cardinals improve to 8-1 and remain perfect in five home games this season.

Stanton will be under center for the Cardinals the rest of the season.

"As far as our football team, everybody in the locker room, including myself, has all the confidence in the world in Drew," Arians added.

Palmer, who missed three games earlier this season with a shoulder injury, had reconstructive surgery on the same knee in 2006 as a member of the Bengals. Both of his ACL tears came just days after signing lucrative contract extensions.

On Dec. 29, 2005, Palmer agreed to a six-year extension with Cincinnati. On Jan. 8, 2006, the Bengals met Pittsburgh in the first round of the AFC playoffs and Palmer lasted just one play, injuring his knee on a 66-yard pass to rookie Chris Henry.

Palmer signed a three-year, $50 million contract extension with Arizona last Friday.

Arians said Palmer is expected to return to football in June or July.