Mountcastle went 1-for-4 with a stolen base in Tuesday's 2-0 loss to the Mariners.
Mountcastle had the Orioles' lone hit Tuesday, and he was also on the front end of a double-steal with Adley Rutschman in the fourth inning. Though he's hit well for much of June, Mountcastle has cooled off by going 3-for-20 in his last five games. He's still hitting a steady .271/.306/.478 with 13 home runs, 38 RBI, 33 runs scored and three steals through 271 plate appearances.