Mariners reportedly promoting top pitching prospect Bryce Miller to start vs. Oakland on Tuesday

According to reports from Joe Doyle of Future Star Series Plus and Daniel Kramer of MLB.com, the Seattle Mariners are calling up their top pitching prospect, RHP Bryce Miller. The righty will make his big league debut as the starter of Tuesday’s game against the Oakland Athletics, slotting into the rotation behind Marco Gonzales and ahead of Logan Gilbert as the M’s rejigger their rotation to handle what is now a season-long loss of LHP Robbie Ray, as well as the disappointing 15-day IL stint at least for RHP Easton McGee after a stellar first start on Saturday. Correspondingly, it would appear, the M’s have DFA’d RHP Diego Castillo, who has already successfully cleared waivers and will remain in Triple-A Tacoma.

Miller is our No. 2 ranked prospect in Seattle’s system here at LL (spoilers for Wednesday’s prospect list finale!). The 24-year-old made several Top-100 prospect lists from major sites, sneaking on at 98th in MLB Pipeline’s preseason ranking and 100th on the dot for Baseball America. The Texan hurler has had a rather striking rise to prominence, rising from JUCO Blinn College up to a bullpen role for Texas A&M, ultimately settling as a swingman in his final season with the Aggies. Things improved quickly from draft day for Miller, who took to Seattle’s player development work naturally, and saw a rise much like that of his new teammate, Matt Brash, a year prior. Starting in Everett in 2022, Miller shredded his way up to the Arkansas rotation, striking out around 30% of opposing hitters on the year. Despite a strong showing in Spring Training, his numbers in four starts this year are more shaky, however as Ryan Divish noted on Twitter, Miller may have been working (or being instructed to work on) specific things in lieu of utilizing his pitches to their fullest capacity.

Though Miller’s frame is a slight 6’2, his four-seam fastball sits in the mid-90s, pushing up to 98 at times and works at the top of the zone to consistent swings and misses.

For all the differences in their physicality, Miller has much in common with Logan Gilbert in their repertoires, as both pitchers seek to pound the fastball first and foremost, even in two-strike counts. Still, Miller’s secondaries have taken the strides to make them separator pitches as well. Both of Miller’s breaking balls tend to hew in the low-80s range, with a sweeping slider and a sharp, vertical 12-6 curve that move with near-perpendicular motion, joined at the axle by his riding four-seam. The curve below helps paint a picture for how Miller keeps lefties off-balance even with a changeup that is not yet consistent.

Miller’s mechanics have improved each year within the organization, consolidating into an athletic, over-the-top offering that nonetheless remains high-effort as Miller’s leaning, whippy arm action makes for a lower release point that still generates excellent backspin, a trait many pitchers have found to be highly effective in generating whiffs. Where the Mount Pleasant, TX native can fall short is on his command. Like Brash before him, Miller’s size is a question mark for his future in the rotation, as some see a high-leverage reliever ultimately. However, Miller appears slated to receive the opportunity to stick in the rotation here, just as George Kirby did in the early days of May in 2022.