Mountcastle is out of the lineup for Wednesday's game against the Marlins.
After going 0-for-8 with three strikeouts in the Orioles' series with the Rangers over the weekend, Mountcastle bounced back with a pair of hits in Tuesday's 6-3 loss to Miami. He'll cede a start at first base to Ryan O'Hearn on Wednesday, but Mountcastle's spot in the Orioles' everyday lineup still appears fairly secure.