SEATTLE – The Mariners went into this offseason with no intention of breaking up a starting rotation that was the best in baseball last season.
Despite their obvious needs on offense and plenty of suitors searching for a young, club-controlled starter, Jerry Dipoto, the Mariners’ president of baseball operations, and general manager Justin Hollander didn’t deviate from their stated objective.
“We are not just hoping to avoid it,” Dipoto said at the end of last season. “On the continuum of A to Z, that would be Plan Z times some denominator. We could shoot ourselves in the foot by trying to get too crafty in what we do. Our pitching is how we’re built. I love our rotation. That wouldn’t be Plan A, but we’ll go into every offseason open to whatever ideas might make us better.”
But Dipoto and Hollander weren’t absolute in their actions. They formulated the workings of possible Plan Zs, listening to trade offers on right-hander Luis Castillo in hopes of getting a MLB hitter in return while also freeing up some added payroll flexibility to add another hitter.
But a trade never materialized.
So the Mariners will have the same quintet of starters that almost carried a flawed team into the postseason. Can they replicate that success in 2025?
We continue to review the Mariners’ position groups entering spring training, here’s a look at the starting pitching.
Projected depth chart
Luis Castillo, RHP; Logan Gilbert, RHP; George Kirby, RHP; Bryce Miller, RHP; Bryan Woo, RHP
Triple-A Tacoma
Emerson Hancock, RHP; Logan Evans, RHP; Brandyn Garcia, LHP; Casey Lawrence, RHP; Blas Castano, RHP
Top prospects
Jurrangelo Cijntje, SP; Ryan Sloan, RHP; Michael Morales, RHP; Tyler Gough, RHP; Ashton Izzi, RHP; Jeter Martinez, RHP
2024 season review
How good were the Mariners starting pitchers last season?
Castillo, Gilbert, Kirby, Miller and Woo started 149 of the Mariners’ 162 games last season, Seattle used only seven starting pitchers all of last season with Hancock starting 12 games and Diaz starting one game. No team in MLB used fewer starting pitchers to get through last season. But those seven starters combined to pitch more innings (942⅔) than any rotation in MLB.
As for the season totals, the Mariners starters combined to lead MLB in ERA (3.38), innings pitched (942⅔), quality starts (92), opponent batting average (. 223), WHIP (1.03), strikeout-to-walk ratio (4.77), fewest walks-per-nine innings (1.77), fewest hits-per-nine innings (7.53), opponent on-base percentage (.266) and opponent OPS (.644).
Gilbert was named the Mariners’ most valuable pitcher by the local BBWAA writers after putting together his best MLB season. He led all of MLB with a career-high 208⅔ innings pitched and WHIP (0.887), two things no other Mariners pitcher has accomplished.
In 33 starts, he posted a 9-12 record with a 3.23 ERA. He was named to the American League All-Star team and finished sixth in the voting for the AL Cy Young Award. He was also the first Mariners pitcher since Felix Hernandez in 2014 to pitch 200 innings and strike out 200 batters in a season.
Reason for optimism
The Mariners’ pitching success isn’t just about the arms on the mound.
Seattle’s “pitching lab” that features pitching coach Pete Woodworth, director of pitching strategy Trent Blank and now assistant general manager Joel Firman has helped instill a culture that’s committed to the craft of pitching.
It’s a continued search for improvement and efficiency while using all of the new data and technology to maximize performance. Gilbert is constantly tinkering with his repertoire, searching for the optimal spin rate, velocity and movement on each of his pitches.
Miller is one of the prime examples of the lab and pitcher combining for success. Last offseason, Miller decided to add a splitfinger fastball, understanding the need for a weapon to combat left-handed hitters. He also made in-season changes to his breaking pitches, making them more viable as swing-and-miss offerings.
The Mariners have the right combination of motivated pitchers willing to make changes and a staff that’s unafraid to mess with success in the search for more of it.
Reason for concern
Unlike most teams, the Mariners’ starting rotation was largely healthy for the 2024 season, with only two pitchers making trips to the injured list.
Woo’s start to the season was delayed by forearm tightness and he missed two weeks during the season with a hamstring strain. Castillo also suffered a hamstring injury late last season, but was expected to be ready to return to pitch in the postseason had the Mariners slid into the wild card round.
But could the heavy workload of starts and innings pitched in 2024 have repercussions in 2025?
Gilbert reached the 200-inning plateau last season after back-to-back seasons of more than 185 innings pitched. Kirby is coming off back-to-back 190-inning seasons while Miller logged 50 more innings in 2024 compared to his rookie of season of 131⅓ innings pitched.
Seattle does have viable depth with Hancock and Evans and Garcia – two of their most-ready prospects – waiting in Triple-A Tacoma.
But a major injury to one of the five projected starters would be crushing.
Breakout candidate
Kirby is a strike-throwing machine who abhors walks. For the second straight season, he led MLB in lowest walks per nine innings (1.1).
But as he’s learned over the past few seasons, there is such a thing as throwing too many strikes, particularly after getting two quick strikes on a hitter. Putting hitters away on pitches outside of the zone is something that doesn’t come natural for him and it’s been an internal struggle to develop that mindset.
It’s a reason for some of his inconsistent outings. But it gradually started to develop for extended periods, leading to brilliance like his outing vs. Arizona where he tossed seven shutout innings, allowing two hits with 12 strikeouts. Going into his third MLB season, Kirby has continued to grow his arsenal of pitches and refine his approach to attacking hitters.