PEORIA, Ariz. -- More than six months after he was called up in the middle of a pennant chase, Matt Brash will finally make his big league debut. 

The Mariners on Saturday announced that the club’s No. 6 prospect and baseball’s No. 98 overall, per MLB Pipeline, has won the No. 5 rotation spot and will break camp with the team. Brash has technically been on the roster since the final week of last season, but didn’t wind up making it into a game. Back then, he would’ve been deployed in a matchup-dictated relief sequence, but the right pocket never manifested.

Now, he’ll remain a starter after putting together arguably the best spring of any Seattle pitcher.

“It definitely motivated me,” Brash said. “I learned a lot from those guys, even though I was only there for a week. So, just kind of being a professional this offseason and taking it super seriously and just keeping my body in shape, keeping my arm in shape. It definitely motivated me to come here and prove myself in Spring Training to earn a spot.”

Brash had been battling with George Kirby for the gig, though Kirby’s chances were more of a longshot, given that his innings accumulation in 2021 was much lower (67 2/3 to Brash’s 97 1/3). He’ll begin the year at Double-A Arkansas, where he finished last season.

“He didn't have a huge workload last year,” Mariners manager Scott Servais said. “It's really important that he continues to progress. George is going to pitch for us this year, there's no question about it. And I think he's going to be a huge part of how our season plays out.”

Brash is in line to start one of the games during Seattle’s second series in Chicago against the White Sox, and in between, he’ll throw an extended bullpen to keep his arm fresh.

“I promised him that if he got on the plane with us that I would pitch him,” Servais said. “And I said, ‘If you accept that, you can go and we'll give you the ball in Chicago.’”

Brash, 23, was the club’s Jamie Moyer Minor League Pitcher of the Year in 2021 after compiling a 2.31 ERA over 20 outings, climbing from High-A Everett to Double-A Arkansas by mid-July. With a wipeout slider/curveball combination -- that has already drawn recognition from acclaimed social media account, PitchingNinja -- and a fastball that sits in the high 90s, he’s flashed some of the most dominant stuff in camp.

Not only does he harness that arsenal well, he has supreme confidence with it and it has baffled big league hitters, lending legitimacy to his off-the-charts Minors numbers. Last year, Brash limited opponents to a .180/.285/.257 (.552 OPS) slash line and struck out 142 for a whopping 35.1 percent rate. He never gave up more than three runs in an outing, including 10 outings of one run or fewer, and he gave up just six homers to 405 batters total. His best outing was on Sept. 2, when he pitched six innings of a combined no-hitter for Arkansas.

When adding up those superlatives, it’s remarkable to think that Brash was a player to be named included from the Padres to complete a 2020 Trade Deadline deal in which Seattle sent reliever Taylor Williams to San Diego. Brash wasn’t even a Top 30 prospect for either team, before or immediately after the transaction, underscoring his rapid ascent.

Yet, the fourth-round Draft pick in 2019 never doubted he’d reach this pinnacle. Brash will become the first player from Kingston, Ontario, to pitch in the Majors among the 258 Canadians to reach The Show.

“It's been quick, for sure, but I always knew I was going to get here at some point,” Brash said. “Just the work ethic I have and the talent I have.”

As for Kirby, who also lived up to his lofty billing this spring, the Mariners will be diligent in how they handle his workload, especially in April. But by having him report to Arkansas instead of Triple-A Tacoma, where weather can be fickle, they’ll be able to better control his schedule.

“You have to be creative,” Servais said. “There may be points in the season where you skip him a start. There may be points where he goes out and throws 40 pitches in a start and you just shut him down. We'll have to be creative with that. There's no blueprint. I think you just have to watch it and you kind of map it out probably a month at a time, trying to make sure he's got plenty of bullets left late."