The Orioles announced that Mountcastle (foot) suffered a "significant" oblique strain while warming up for his first rehab game and will now be out a couple of more months, Jake Rill of MLB.com reports.
Mountcastle, who has not played since April 11, will miss even more time after straining his oblique prior to his first rehab game. Orioles general manager Mike Elias said they "can't expect him back anytime soon." The 29-year-old is now unlikely to play again this season after registering just eight games played from late March to early April.