Alec Ogletree scored a touchdown on an interception return, but he left for the locker room soon after. The Rams linebacker shook his head at teammates as he walked off the field.
He has a left elbow injury, and the Rams list him as questionable to return.
Ogletree, who replays plays to his teammates from defensive coordinator Wade Phillips, was replaced by Bryce Hager.
Ogletree had a tackle, a defensed pass and an interception he returned 41 yards for a score to give the Rams a 16-0 lead.
The Cardinals have come back with a pair of touchdowns, but missed an extra point, to cut the Rams’ lead to 16-13 late in the second quarter.