SEATTLE – Colton Cowser was reinstated from the injured list yesterday and he’s playing center field tonight and batting sixth for the series opener in Seattle.

Jackson Holliday remains the leadoff hitter.

Coby Mayo is the designated hitter, Heston Kjerstad is in right field and Dylan Carlson is in left.

Ryan O’Hearn, the cleanup hitter and first baseman, is batting .329 against right-handers and the Mariners are starting three in the series. O’Hearn’s average is tied for fourth-highest among left-handed hitters versus right-handers in a minimum 100 plate appearances.

Tomoyuki Sugano has posted a 3.23 ERA and 1.063 WHIP in 11 starts. He’s got a 3.67 ERA and 1.223 WHIP in six home games and a 2.73 ERA and 0.876 WHIP in five road games.

The Orioles placed Ryan Mountcastle on the 10-day injured this this morning with a right hamstring strain and recalled corner infielder Coby Mayo.

That wasn’t the extent of the changes.

Outfielder Jordyn Adams had his contract selected and he’s wearing No. 80. Catcher Chadwick Tromp was designated for assignment.

Mountcastle exited last night’s game in the top of the eighth inning, after stealing home in a 2-1 win over the White Sox. Interim manager Tony Mansolino said Mountcastle would be re-evaluated this morning.

A roster battered by injuries can’t get healthy.

The unpredictable nature of the Orioles is still setting traps.

Adley Rutschman avoided the seven-day concussion list, serving as designated hitter Wednesday and starting behind the plate yesterday. The Orioles usually don’t carry three catchers until rosters expand in September, and the next decision appeared to come down to whether they'd designate Chadwick Tromp for assignment or option Maverick Handley. One of them would step aside for the next reinstatement - whether Colton Cowser, Jordan Westburg or Ramón Laureano.

Cowser singled and walked twice last night at Triple-A Norfolk, and Westburg had a single and double.

Cedric Mullins wasn’t supposed to go on the injured list. Cooper Hummel wasn’t supposed to keep his locker in the home clubhouse. He hadn’t used it until yesterday because the Orioles signed him Sunday while in Boston and designated him for assignment the following day.

News of Hummel's return led to assumptions about the backup catchers, but they proved to be nothing more than a Tromp trap. A Handley hazard. 

The Orioles optioned reliever Colin Selby to Triple-A Norfolk today and activated pitcher Scott Blewett, who was claimed on waivers yesterday from the Twins.

Selby allowed two runs and three hits in his only inning in Arizona after the Orioles recalled him Wednesday as the roster replacement for Zach Eflin, who’s on the injured list with a right lat strain.

Blewett, who turned 29 five days ago, was designated for assignment again on Saturday after the Twins selected his contract earlier in the week and he allowed one run with five strikeouts and no walks in 4 2/3 innings. He’s made 19 relief appearances in the majors and posted a 2.18 ERA in 33 innings.

Blewett is wearing No. 67.

The Orioles signed catcher Chadwick Tromp to a minor league deal on Sunday. They faced him a few times in spring training with the Braves.