A key piece of the Orioles infield will be out for at least the next week.

Ryan Mountcastle was placed on the injured list on Monday with vertigo. The Orioles selected the contract of catcher Mark Kolozsvary from Triple-A Norfolk to replace Mountcastle on the active roster and designated RHP Noah Denoyer for assignment to make room on the 40-man roster.

Mountcastle has not played since June 8, the team initially saying he was just under the weather. The timing of the move was a surprise — manager Brandon Hyde said prior to the game that Mountcastle was feeling better and could be available off the bench Monday night.

Mountcastle is hitting .227 with 11 home runs this season.

Ryan O’Hearn and Josh Lester will take over duties at first base. Anthony Santander is also capable of playing there if needed.

With Kolozsvary added to the roster, the Orioles will carry three catchers again, returning to the system they tied out earlier this season. By carrying an extra catcher, the Orioles can put Adley Rutschman in the lineup every day, either as designated hitter or as the backstop, while ensuring the team also has a catcher on the bench.

Kolozsvary made his MLB debut last season with the Reds. He was claimed off waivers by the Orioles in October and has played 25 games for Norfolk so far this season, hitting .172.

Denoyer was their No. 27 prospect according to MLB pipeline. He was added to the 40-man roster last offseason to protect him from the Rule 5 Draft.

Tate, Givens to begin rehab assignments

Relievers Dillon Tate and Mychal Givens are one step closer to a return.

Tate started the season on the injured list with a flexor strain, then suffered a stress fracture in his elbow while he was building up. He will now head back out on a rehab assignment, and is scheduled to pitch for Norfolk on Thursday and Saturday.

Givens will also begin another rehab assignment. He will pitch for Double-A Bowie on Wednseday and Norfolk on Saturday. Givens has pitched in just six games this season, missing time with a knee injury and now shoulder inflammation. He’s given up five earned runs in four innings pitched this year.

danielle.allentuck@thebaltimorebanner.com

This story has been updated to correctly identify Josh Lester.