Cooper (triceps) is starting at first base and hitting third Thursday against the Cardinals, Joe Frisaro of MLB.com reports.
Cooper was scratched from Wednesday's lineup due to a sore triceps, but he's good to go after getting the day off. The 28-year-old has been locked in at the plate since returning from the injured list in mid-May, slashing .331/.401/.521 with six homers and 21 RBI in 32 games.