SCOTTSDALE, Ariz. -- Matt Brash had a tangible taste of the big leagues on a grand stage without actually taking the platform, and it left him all the more eager for 2022.

Seattle’s No. 9 prospect and baseball’s No. 98, per MLB Pipeline, Brash watched the Mariners’ late-season playoff push with one of the best seats in the house, the home bullpen at T-Mobile Park, after being called up during the final week. Yet he never wound up in a game due mostly to matchup circumstances, which resulted in a somewhat anticlimactic finish to his breakout season.

“Even just walking out on the field, going to the bullpen, I'll never forget it,” said Brash, who was recognized as the Mariners’ Jamie Moyer Minor League Pitcher of the Year for 2021. “Just how electric it was in there and everyone with their ‘Believe’ signs and all that. It just shows that they're really behind the Mariners, and I hope I get to experience that someday.”

Brash made the first start of his first big league Spring Training on Monday -- in a 9-1 loss to Arizona -- throwing two scoreless innings and surrendering just one hit and one walk among eight batters faced. His lone strikeout was impressive, a high-90s heater up and away that blew right by the D-backs' Drew Ellis.

Brash also flashed the elite slider that has some in the scouting circles suggesting that it has potential to be the best pitch in the Mariners’ organization. Because Monday’s game was at Salt River Fields -- the only Cactus League facility that has Statcast tracking -- there was finally public data to pair with the eye test, and the results were off the charts.

Brash threw 10 sliders that averaged 2,865 rpm, well above the big league average of 2,417 rpm in 2021, topping out at 3,158 rpm, which is the highest recorded in baseball this spring. Again, there’s only one Cactus venue that has such data in Spring Training, but it nonetheless stood out.

Brash learned how to throw the slider from a teammate during his final year at Niagra (N.Y.) University in 2019, leveraging his already elite ability to spin a baseball with a new offering that was missing bats at an unreal rate. That’s what stood out when the Mariners acquired him from the Padres in 2020 -- as a player to be named later, to boot.

As he’s added significantly more velocity -- he averaged 97.1 mph and topped out at 98 on Monday -- the slider has developed more pronounced swing-and-miss behaviors. 

“I have a really great feel for it,” Brash said. “I throw it in any count and don’t try to force it. I don't try to do too much. I know my shape, and I know it's going to break. So I kind of just fall on conviction, every pitch. I think that's why I get the effect that I do.”

Despite being a mostly two-pitch pitcher, Brash intends to remain a starter long term, which has led to him better establishing a work-in-progress changeup, which he threw just once on Monday. He also mixes in a knuckle curve, which he says has similar tendencies to the slider and often gets mistaken for it.

“I think I could be a starter with the fastball, slider and curve as it is right now, but the changeup just kind of brings me to the next level,” Brash said. “And especially against lefties, it’s just another look. So I mean, if I can land four pitches in the zone, which I know I can, I know good stuff is going to happen.” 

As it stands, and unless the Mariners add an impact starter, the final rotation spot is up for grabs, with Brash, Levi Stoudt and George Kirby in consideration, all of whom have big potential yet no MLB experience. Mariners president of baseball operations Jerry Dipoto has hinted that Brash -- who had a 2.13 ERA and 35.1% strikeout rate last year while climbing to Double-A -- is leading the way.  

“I'm going for the spot,” Brash said. “I’m not focused on it too much. I mean, I'm just doing my thing, trying to get the experience, learn from the older guys. I mean, being in big league camp is enough, like learning so much from these guys. It’s been such a great experience so far. But, I’m always competing. It’s always like a tryout here, like a training camp, and I’m trying to show what I’ve got.”