GLENDALE, Ariz. -- Los Angeles Rams wide receiver Cooper Kupp injured his ankle in the second quarter of Sunday's game against the Arizona Cardinals and is doubtful to return.

Kupp appeared to sustain the injury on his fourth reception of the game -- a 24-yard catch-and-run near the end of the first half. He walked off the field to the locker room at halftime with a noticeable limp.

The Rams are already without wide receiver Puka Nacua, who is on injured reserve after spraining his posterior cruciate ligament in Week 1.

Kupp had four catches for 37 yards on six targets against the Cardinals before leaving the game.

In two games this season, Kupp has 18 catches for 147 yards and a touchdown.