The Mariners Are Going to Have a Tough Decision to Make Soon
With Seattle about to have one of their key starting pitchers return soon, it leaves them with a touch choice to make regarding the rotation.
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You can never have too much depth. As injuries continue to increase year over year, that old saying has never been more true.
A team can have effective starters and backups at a position and even a decent reinforcement waiting in the wings down in the minors. A couple injuries later, that same team is trying to get by without having to scan the market for a replacement.
The Seattle Mariners found themselves in this realm to start the 2026 season. And it came in an area that has been a traditional strength of theirs, the starting rotation.
Their first hit to the unit came during the offseason when Logan Evans, a rookie in 2025, had Tommy John surgery which leaves the Mariners without his services this season.
The next one came in the form of 27-year-old Bryce Miller. Looking to improve from a disappointing 2025 season, he has been out since spring training with an oblique injury.
So Seattle set off with a rotation consisting of George Kirby, Bryan Woo, Logan Gilbert, Luis Castillo, and Emerson Hancock. Each pitcher made at least 16 starts last year, but that also left no more pitchers on the roster who made a start for the Mariners in 2025.
Seattle has so far kept their heads above water quite well. The team is 13th in the league in starters’ ERA at 4.01 and three of the starters in the rotation have personal ERA’s of 4.03 or less.
The most surprising of those three is Hancock, the 26-year-old who has a dazzling 2.59 ERA with 46 strikeouts to just six walks to start the season. On the other end of the spectrum is Castillo, who is in his 10th season and struggling hard for the first time with a 6.29 ERA in his first seven starts.
Soon enough, though, Miller is going to come back into the equation. He is progressing well in his recovery, is expected to throw 65-70 pitches in his next rehab start on Wednesday, and it won’t be much longer than that until he is reinstated by the team.
And that leads the Mariners to a tough decision: what do they do with Miller? How do they handle the rotation? It’s a good problem for a team to have and Seattle has a few different routes in which they could go.
Reinstate Miller, Option Him to Triple-A Tacoma
Optioning Miller to Triple-A would be the easiest solution. Since having his contract selected early in the 2023 season, he hasn’t been sent back to the minors since, so all three of his minor league options remain.
It would also be understandable if the Mariners wanted more time to be sure Miller is ready to go back into the rotation. He struggled to a 5.68 ERA in 18 starts last year while fighting elbow inflammation and is now attempting to come back from a new injury.
The problem is that Miller is looking pretty darn good. Over his two most recent rehab starts, he has pitched seven scoreless innings and given up just three hits and three walks while striking out 10.
Miller at his best is one of the best pitchers in the AL and if his velocity is back to normal (it was down about a half mph for most of his primary pitches last year), then his best landing spot might still be in the Mariners rotation. So then how does Seattle make room for him?
Move Castillo to the Bullpen
Castillo has been the rock of the rotation for either the Reds or Mariners for the better part of a decade. He has a career 3.62 ERA, has made three All-Star games, and his 26.8 fWAR since 2017 is 10th among 393 qualified pitchers.
He’s had a rough go if it in 2026, however. He’s given up three or more earned runs in four of his seven starts to begin the season. Seattle has won just two of the games Castillo has started.
And it doesn’t help that all of his pitches are getting ambushed. Castillo is giving up a .293 average and .517 slugging percentage off his four-seamer versus .203 and .411 last year, respectively, as well as a .294 average and .471 slug versus 2025’s .230 and .336 on his slider.
A move to the bullpen would be a huge adjustment for Castillo as he’s started in all of his 250 career MLB appearances. So if Seattle doesn’t want to do that, then they could go the unorthodox route.
Six-Man Rotation
Teams usually only go with six-rotations for a specific reason. Perhaps one of the starters needs a couple extra days of rest and the team doesn’t want to mess with the other starters’ schedules. Or maybe a team is looking at a lot of games with minimal days off in their future.
The Mariners are coming up on the latter situation. They only have three days off for the entire month of May and four days off between now and June 15.
On the bright side, the schedule isn’t that hard. Only three of Seattle’s 12 series between now and the middle of June are against teams that currently have winning records (Braves, Padres, Athletics).
Whether it’s six-man rotation or someone being the odd man out, the Mariners will have a decision to make soon. Honestly, though, there are plenty of teams who only wish they had such a tough choice to make.
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Written by
Matt Carroll is a writer for Just Baseball and former site expert at Reviewing the Brew. He studied journalism at the University of Wisconsin-Madison and currently…