SEATTLE -- Top pitching prospect Justus Sheffield was added to the 25-man roster on Friday and will make his Mariners debut in relief of Yusei Kikuchi as the club begins its plan to limit Kikuchi’s workload in his first season in the Majors. To make room for Sheffield, the Mariners designated right-hander Shawn Armstrong for assignment.

The 22-year-old Sheffield, acquired from the Yankees in the James Paxton trade, has made three appearances for Triple-A Tacoma (0-1, 3.93 ERA), including a 46-pitch, three-inning stint out of the bullpen on Monday after an “opener” inning by reliever Matt Tenuta.

That trial run was to give Sheffield a chance to prepare to follow Kikuchi, who will be limited to one-inning starts about once a month to help him adjust from the typical once-a-week pitching rotation in Japan.

Kikuchi is 1-1 with a 4.68 ERA in his first six MLB starts, but now will get a bit of a break with the shorter outing.

“The way [Sheffield's] looking at it and I’ve told him, ‘Get ready for your start like you’re going to go out and throw 95 pitches. You’re just not going to,’” manager Scott Servais said. “You don’t have to try any harder. Go through your pregame meeting just like always, things like that. Hopefully he throws a good inning.”

Sheffield will be pitching on three days’ rest since his relief stint on Monday, so Servais said he won’t be extended too long, either.

“He’s not going to throw 100 pitches,” Servais said. “Just try to get us to the point in the ballgame where we can go to the bullpen and go from there. That would be the goal.”

Sheffield, the Mariners' No. 1 overall prospect, per MLB Pipeline, made his MLB debut for the Yankees as a September callup last year, pitching 2 2/3 innings in three relief appearances while allowing four hits and three runs.

When a player's contract is designated for assignment -- often abbreviated "DFA" -- that player is immediately removed from his club's 40-man roster, and 25-man roster if he was on that as well. Within seven days of the transaction (it was previously 10 days), the player must either be traded, released or placed on irrevocable outright waivers.

Bruce ready to return from sore quad

Jay Bruce wasn’t in the Mariners' starting lineup for a fourth straight game on Thursday due to a sore quadricep muscle in his left leg, but the 32-year-old outfielder is close to 100 percent and could be back in the lineup by Friday.

Bruce, acquired from the Mets in December, leads the Mariners with nine home runs in his first 22 games, but has been limited to just one pinch-hitting appearance on Sunday in Anaheim since feeling his leg tighten up while chasing down a fly ball down the right-field line at the end of Saturday’s game.

“We’ll give him one more day,” Servais said prior to Thursday’s series opener against the Rangers. “He said yesterday he was about 80 percent. I want to get him 100 percent. I don’t want to play him two days and then all the sudden have a setback.”

The three-time National League All-Star has posted a .208/.287/.597 line with three doubles and 16 RBIs and has already equaled his home run total in 94 games last year in an injury-plagued season with the Mets.

So getting and staying healthy is an important thing for the Texas native.

“These things can be tricky, so we want to make sure we’re out in front of it and not playing catch-up,” he said. “I feel good, but Scott wanted to give me one more day to just kind of put the nail in it for me. That’s probably smart. As badly as I want to be out there, missing a fourth game is better than having to miss 10-12 [games] or two weeks.”

Bruce needs one home run in the four remaining games this month to become just the fourth Mariner in team history with 10 homers by the end of April. The only players to do that have been Ken Griffey Jr. (13 in 1997 and 11 in ’98), Nelson Cruz (10 in ’15) and Mitch Haniger (10 last season).

Worth noting

• Right-handed reliever Mike Wright, acquired from the Orioles on Wednesday, likely won’t join the Mariners until Friday night or Saturday. Players have 72 hours to report, which would give the Mariners a chance to activate Sheffield for Friday’s game and then option him back to Tacoma before adding Wright to the 25-man roster.

• Veteran left-hander Jon Niese has signed a Minor League contract with the Mariners and will report to Triple-A Tacoma. The 32-year-old was 69-68 with 4.07 ERA in nine seasons with the Mets and Pirates, but hasn't pitched in MLB since '16. He was in camp with the Yankees in '17 and Rangers in '18, but released before the season began. Niese was with the independent Long Island Ducks this spring before signing with Seattle.

• The Mariners also re-signed veteran right-hander Tyler Cloyd to a Minor League deal and he was slated to start Thursday for Tacoma. Cloyd, 31, pitched for Tacoma in 2017 and also made one relief appearance that year for Seattle, then was in the Marlins organization last year.

• After missing 13 days with a strained hip flexor, first baseman Evan White -- the Mariners’ first-round Draft pick in 2017 -- has been activated off the injury list and is back playing for Double-A Arkansas.