Coach Ken Whisenhunt said Leinart, the team's first-round pick
in 2006, would be out indefinitely.
"We don't know how long it's going to be," Whisenhunt said.
"But it's going to be for an extended period of time."
Leinart returned to the sideline after halftime, wearing a
T-shirt and shorts and with his arm in a sling. A team spokesman
said Leinart had no comment.
Leinart was hurt on a sack for a 9-yard loss by blitzing Rams
linebacker Will Witherspoon, which knocked the Cardinals back to
their 7. He was replaced by Kurt Warner, who earlier in the second
quarter led the Cardinals to their first touchdown.
Leinart walked off the field with his left arm held close to his
chest. He was 7-for-13 passing for 100 yards and an interception.