Mariners: Bryce Miller set for Debut

Mariners Bryce Miller
(Abbie Parr/The Associated Press)

The Seattle Mariners are shuffling their pitching staff. They will select the contract of Bryce Miller, who is currently the Mariners No. 2 prospect per the MLB pipeline. The report was first announced by Joe Doyle of Future Star Series. In a corresponding move, Diego Castillo has passed through waivers and the team has assigned him outright to Triple-A Tacoma.


With that outright, Castillo is no longer on the 40-man roster. With three years of MLB Service time, he has the ability to decline the outright. However, he doesn’t have five years of service so rejecting the assignment would result in forfeiting the remainder of this year’s $2.95MM salary. He’ll most likely accept the assignment, due to those circumstances. Over the past three years, Castillo has proved himself to be an integral piece to the ‘Los Bomberos‘ but has been declining since being one of the best relievers in baseball in 2019. Castillo was quite effective in his first season and a half with the Mariners, pitching to a 3.42 ERA with an above-average 25.5% strikeout rate against a slightly below-average 9.4% walk rate. He held opponents to just a .196 average, yielded only 1.06 HR/9 and kept the ball on the ground at a 48.5% clip.

The 2023 season has been disastrous for the 29-year-old though. In 8 2/3 innings so far, he’s walked as many batters as he’s fanned (seven) and also plunked a hitter. He’s also surrendered two home runs in that span and a total of six runs. The Mariners have been waiting for Castillo to turn it around, but likely saw his struggles as a way to open up a 40-man roster spot.


Bryce Miller is set to make his Major League Debut for the Mariners. The 24-year-old appeared to be lights out in spring training but has struggled since being sent to Double-A, pitching to a 6.41 ERA in 19 2/3 frames. Miller last pitched on April 25, so he’s well-rested.

The handful of shaky outings this season, doesn’t appear to waiver the Mariners’ confidence. They’ll hope that he can follow in the steps of Logan Gilbert and George Kirby. As the Mariners have already lost Robbie Ray for the season and have seen Chris Flexen struggle in the rotation. This led to the earlier call-up of Easton McGee, who pitched 6 2/3 scoreless innings in his debut.

Miller is seen as a potential mid-rotation starter, thanks in no small part to a heater that sits upper-90s and can bump 100 mph. He pairs that with a slider and changeup, and the former college reliever has improved his command as the Mariners have stretched him back out as a starter.

If Miller sticks in the big leagues, he’d be on pace to qualify for arbitration as a Super Two player following the 2025 season and reach free agency at the conclusion of the 2029 season. Of course, future optional assignments could alter one or both of those timetables considerably.


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