Bryce Miller is the newest Mariners' starter ready to breakout

The Mariners' pitching lab is poised to produce another young All-Star in Bryce Miller. Miller, who has a 70-grade fastball, added a splitter over the offseason that could take him to the next level.
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Seattle Mariners Photo Day / Steph Chambers/GettyImages

Bryce Miller was a much-discussed trade candidate this winter across the league, as a young proven MLB starter with six years of team control, which is the most valuable commodity in front offices these days. Miller had a 3.97 before the All-Star Break with a .262 wOBA, which is at least middle of the rotation production considering the MLB average is around a 4.30 ERA.

A 3rd pitch to Bryce Miller's arsenal could be a gamechanger

Post All-Star break, however, Miller did slip with a 4.60 ERA and his BAA (batting average against) shot up from .203 in his first half to .282 down the stretch. It's not uncommon for a young pitcher to wear down in his first MLB season, particularly considering he threw over 150 innings for the first time in his career. However, one thing that became apparent was Miller's reliance on his dominant fastball, and his lack of a third pitch he can rely on. He threw his fastball 58.5% of the time in 2023, with Bryce throwing his slider about 19% of the time.

Miller's slider held up against Major League hitters last season, with opponents hitting .202 against it, albeit with a .253 xBA. Miller's fastball had a whiff rate of 27.1%, and it registered as 10th best in the MLB with a 121 stuff +. The slider also ranked well with a 113 stuff+, but it is a limited sample size.

We've seen fastball/slider guys carry reliever risk, and the splitter Miller added could significantly mitigate his reliever risk and provide job security in the rotation. We see young starters try to develop that third pitch, but most of them don't have a 70-grade fastball. If Miller can keep hitters off balance with a plus slider and reliable splitter, the fastball will play up and he'll have frontline starter potential.

ZIPS projects a 3.88 ERA for 2024, with Steamer expecting a 4.32 from Miller over 142 innings. However, these numbers have Miller's fastball/slider reliance baked in, with a curveball and changeup that are still a bit underdeveloped. If Pete Woodworth and the Mariners' staff can help Miller hone that splitter, we're talking about ace potential. The Mariners have arguably the best rotation in the American League with Miller considered a back-end starter, but the sky is the limit for this club if Bryce takes it to the next level.