Mountcastle (illness) will serve as Baltimore's designated hitter and bat fourth Wednesday against the Mariners, Roch Kubatko of MASNSports.com reports.
After missing two games while fighting off an illness, Mountcastle will now return to the starting nine against Logan Gilbert and the M's. Mountcastle had gone 4-for-17 with an RBI and a run scored in his last five games before getting sick.