GLENDALE, Ariz. (AP) - Carson Palmer was carted off the field after injuring his left knee in the fourth quarter and the Arizona Cardinals rallied minus their quarterback, beating the St. Louis Rams 31-14 Sunday to improve the best record in the NFL.
After Palmer went down, backup Drew Stanton and the Arizona defense spurred the Cardinals with three touchdowns over a span of 3 minutes, 48 seconds.
"We don't know anything about Carson's injury or the length, whatever it is yet," Arizona coach Bruce Arians said. "It is obviously a knee. He will be evaluated and get an MRI and everything and we will know something by tomorrow and hopefully by Tuesday."
Rookie John Brown's diving grab of Stanton's 48-yard touchdown pass put the Cardinals (8-1) up 17-14 with 7:40 to play. The pass came on the first series after Palmer hurt his knee while trying to avoid the rush.
Palmer was able to walk off the field but a short time later was taken to the locker room on a cart.
It was the same knee Palmer injured Jan. 8, 2006, in a playoff game against Pittsburgh, when he tore his ACL and MCL on his first pass of the game.
Patrick Peterson got his first two interceptions of the season, returning the second one 30 yards for a touchdown to make it 24-14. Moments later, Austin Davis fumbled and Antonio Cromartie returned it 14 yards for a score as Arizona outscored the Rams 21-0 in the fourth quarter.
St. Louis (3-6) was shut out in the second half.
At 8-1, the Cardinals have their best record after nine games since going 11-1 as the Chicago Cardinals in 1948.
Palmer's injury loomed over everything, though.
He was playing some of the best football of his career and, on Friday, signed a three-year contract extension worth a reported $50 million with $20.5 million guaranteed.
On third at the Rams 28, Palmer dropped back to pass, then tried to avoid blitzing safety Mark Barron. The quarterback's leg gave way and Barron touched Palmer for a sack.
Stanton went 2-1 as a starter earlier this season when Palmer was out with a damaged nerve in his throwing shoulder.
"Everyone has confidence in Drew," Arians said. "Nothing drops off."
Palmer was 25-of-36 for 241 yards, with no touchdowns and just his third interception of the season.
Arizona's Larry Fitzgerald caught nine passes for 112 yards.
Davis completed 17-of-30 for 216 yards and a TD with two interceptions and a lost fumble.
On Peterson's second interception, the ball bounced off the hands of the Rams' Kenny Britt. Peterson caught it and raced to the end zone for the score. On St. Louis' next possession, Kareem Martin hit Davis and the ball came free as he tried to pass. Cromartie picked it up and ran in for the score to put Arizona up 31-14 with 3:58 to play.
Arizona has outscored opponents in the fourth quarter 91-34.
After entering the game, Stanton completed an 11-yard pass to Rob Housler, ran for 4 yards, then completed a 26-yarder to John Carlson on his first three plays. Then Stanton let fly for the speedy Brown, who beat defenders and laid out to catch the ball as he crossed the goal line.
Jared Cook, who caught seven passes for 141 yards and two touchdowns against Arizona in last season's opener, got behind rookie Deone Bucannon for a 59-yard touchdown pass with 1:50 left to give St. Louis a 14-10 halftime lead.
The TD came after Arizona had scored 10 straight points to take a 10-7 lead on Chandler Catanazaro's 43-yard field goal with 4:52 left in the half. With the kick, Catanazaro tied the NFL record for consecutive field goals to start a career at 17 before missing a 53-yarder on the play after Palmer was hurt.