Luis Castillo is gone, and the Seattle Mariners will have a new veteran buffer at the top of their rotation. It’s not like they’re scrambling for more arms. The Mariners still have more starting-pitching talent than most organizations.
What changes in 2027 is the distribution of responsibility. This rotation now belongs completely to the homegrown core, and the money saved in the Castillo trade needs to show up somewhere in the lineup.
How the Mariners’ Starting Rotation Could Look in 2027
- Logan Gilbert
- Bryan Woo
- George Kirby
- Bryce Miller
- Kade Anderson
This may not feel like the most reasonable projection using only the pitchers currently in the organization. The first three spots feel secure. The final two carry more uncertainty, with Emerson Hancock positioned as the immediate alternative and Ryan Sloan continuing to climb behind them.
Gilbert (12-11, 4.73 ERA over 186 innings) certainly belongs at the top. With Castillo out of the picture, there’s little reason to dance around whose rotation this should be. Gilbert brings the stability, innings, strikeouts and presence the Mariners need from a staff leader.
His contract situation also becomes one of the front office’s biggest decisions. Gilbert is moving through the expensive end of arbitration, and Seattle cannot afford to let his future drift. The Mariners should pursue an extension first. If those talks go nowhere, then trade discussions must pick up. For now, he’s still a Mariner and he should be the 2027 Opening Day starter.
Woo (12-10, 4.01 ERA over 173 innings) gets the second spot because his performance has moved him beyond the upside conversation. He already looks like a front-line starter when he’s right.
The next step is workload. Seattle needs Woo healthy enough to take the ball throughout the season and pitch deep enough into games to ease the burden on the bullpen. If Woo provides a full season, he could challenge Gilbert for the top spot rather than simply settle in behind him. But 2027 needs to see Woo complete what they call the “next step.”
Kirby slides to third, which says more about the strength of this rotation than it does about his ceiling. His best version could put him and Gilbert into a 1A and 1B type of conversation. We just didn’t see that version (9-11, 4.33 ERA over 174 2/3 innings) consistently enough to rank him ahead of Woo.
Seattle needs to help Kirby recover the clean identity that made him special. We recently covered some issues with his arsenal in 2026. He doesn’t need another pitch added to it. He needs a better plan.
Miller (4-10, 4.17 ERA over 118 2/3 innings) might be the rotation’s biggest variable. His 2024 season showed how good he can be when healthy. He covered 180 1/3 innings, posted a 2.94 ERA and looked like another long-term fixture produced by Seattle’s pitching operation. His injury-plagued 2025 season changed the conversation, and 2027 will require more than memories of what he did three years earlier.
We still have Miller fourth because the arm talent warrants the bet. Spring training will play a big role. He needs to arrive healthy, command the baseball and show that his arsenal can handle a lineup multiple times. If he looks right, Seattle has one of baseball’s deepest rotations again. If he doesn’t, Hancock becomes difficult to keep out of the conversation.
Kade Anderson Has Earned His Shot in the Starting Five
Seattle pushed him from Double-A into a major-league playoff race less than 14 months after drafting him third overall. He responded with enough poise and quality to show that he belongs in the Opening Day rotation discussion.
There will be uneven starts. Anderson (2-2, 3.79 ERA over 35 2/3 innings) is still a young pitcher learning how to retire major-league hitters every fifth day. His upside makes those growing pains worth accepting. He also gives Seattle something different as the lone left-hander in a projected rotation filled with righties.
Hancock appears to be the odd man out, although that doesn’t make him expendable. A multi-inning bullpen role could fit him well. Hancock can cover the middle innings, rescue the bullpen when a starter exits early and remain stretched out enough to step back into the rotation. That job would give Seattle practical depth without forcing six starters into five seats.
It would also create some healthy pressure on Miller and Anderson. Neither should arrive in Peoria with a guaranteed spot in the rotation.
Sloan is the next name to watch. His progress gives the Mariners another high-upside starter who could eventually force the issue. However, he’s part of the organization’s future. He doesn’t make any established starter expendable.
This projection can change quickly. Seattle could trade from its rotation to acquire the impact bat its lineup still needs. An offseason addition could reshape Hancock’s role and/or Sloan could kick down the door earlier than expected.
For now, Gilbert, Kirby, Woo, Miller and Anderson represent the strongest five.
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