For years, the Mariners’ rotation, especially at home, has been one of the league’s most envied. Logan Gilbert, George Kirby again Bryan Woo they’ve all made the All-Star team in the last few years. All three have a career ERA of 3.61 or better with better than average strikeout and walk rates alike. Bryce Miller he didn’t have as much success against his peers, but he posted a quality 3.52 ERA and walk rates in his first 56 MLB starts before the injury-ravaged 2025 season (90 1/3 innings, 5.68 ERA, two IL stints with elbow inflammation).
Veteran is right Luis Castillo he wasn’t signed and developed by the Mariners, but Seattle traded him away from Cincinnati in 2022 in a package headlined by infield prospects. Noelvi Marte again Edwin Arroyo. The M’s immediately extended Castillo to a five-year, $108MM deal. In parts of five seasons with Seattle, his 3.61 ERA is right in line with the previously mentioned team (and almost identical to his 3.62 mark in six seasons with the Reds).
No organization in baseball has been going around the major leagues more than the Mariners since this wave of marauders arrived on the scene at T-Mobile Park. They have been consistent, productive and, barring Miller’s recent injury issues, durable. That’s been key for the Mariners, because one thing that gets talked about a lot about their strong rotation is that the team’s depth hasn’t been great.
From 2022-25, the quintet of Gilbert, Kirby, Woo, Miller and Castillo started 75% of the Mariners’ games. (Castillo was not acquired until July 29 of the 2022 season.) The Mariners had rotation cameos. Robbie Ray (signed a five-year deal, missed second season due to Tommy John surgery, then traded to Giants), Chris Flexen (26 starts at the end of his low contract) and Marco Gonzales (a holdover from a previous replacement group that ended up being sold damaged). But for the most part, it’s been the same group of five, which has helped mask the fact that many of their top prospects in recent years have all been position players.
Another hopeful addition to the team, for years, was the right-hander Emerson Hancock. 6th overall pick in 2020, Hancock was not considered the ace of the future. He was an improved college arm with above-average stuff and good command, whom Baseball America named the No. 1 prospect. 3 — “and perhaps better if he refines his breaking pitches.”
Instead, Hancock’s development went in the opposite direction. His command was terrible. He lost his life on his fastball as he battled shoulder problems and a lat strain. In general, he became more hittable. Hancock’s strikeout rate dropped when he reached Triple-A in 2024, though he still posted an ERA in the mid-3.00s. He was north of 5.00 in 2025.
Between regular and consistent major league outings from 2023-25, Hancock totaled 162 2/3 innings with a 4.81 ERA, one of the lowest strikeout rates in baseball (15.6%) among pitchers with those innings and a poor walk rate (7.8%). He looked like a fifth or sixth starter — the kind of arm that swings in and out of the swing before settling into a bullpen role or starting to bounce around the league as a pitcher.
There weren’t many visible signs of an outbreak last year. Hancock’s fastball average climbed to 94.9 mph, though that was at least moderately skewed toward the ‘pen later in the season. He averaged 94.6 mph as a starter in 2025 — still up from his previous career-best 93.4 mph — and 97.2 mph as a reliever. But even with the increased velo, Hancock’s swing rate decreased. The contact level of his opponents has increased. His 8.1% walk rate was a career-worst mark. Hancock had the look of a depth starter and was entering his final option year in 2026. The long-term outlook was not good.
And then spring training rolled around.
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