Cooper will start at first base and bat eighth in Wednesday's game against the Marlins.
Cooper has largely served as a short-side platoon player between first base and designated hitter with the Padres, but he's carved out a larger share of the playing time versus right-handed pitching since Ji-Man Choi (rib) was placed on the 10-day injured list Aug. 14. Since Choi played his last game Aug. 11, Cooper has started nine of the Padres' subsequent 12 games, and two of those absences came over the weekend while Cooper dealt with a wrist injury.