Seattle Mariners starting pitcher Luis Castillo struggled again on Monday night, giving up seven earned runs in five innings as the M's lost 11-4 against the previously reeling Minnesota Twins.

Seattle is now 14-16 and missed an opportunity to get back to .500, while also putting themselves against the wall in terms of trying to win this series.

Castillo's struggles are nothing new. He has an ERA over eight in his last five starts, surrendering 35 hits in his last 22.1 innings. He's also given up four home runs and walked nine in that time. The velocity has generally been good, but the quality of stuff has decreased, and his ability to generate swing-and-miss is waning, as evidenced by his only 19 strikeouts in those 22.1 innings.

To Castillo's credit, it's clear that he and his catchers are trying to find a way to get through these outings with more success, but no one has found the right formula yet. 

For the record, I've said that I think Castillo is a guy can that still remain competitive, but that you generally hope to get through five innings with only two or three runs allowed. There will be some outings that look better than that, and some that look a lot worse, and there will be a lot in the middle that widely vary. That's just the nature of being 33 and having the miles on the arm that Castillo does.

But for a Mariners team that is looking to win another division title, there are some discussions to be had about Castillo's role moving forward, especially as Bryce Miller works back from an oblique issue.

Let's dive in.

Miller likely has three rehab assignments left, meaning he's probably three weeks away from a return. So for now, the Mariners don't have to make a decision. It's that simple. A lot can happen in three weeks to change the calculus. Castillo could figure it out. Someone could get hurt, forcing him to stay in the rotation.

The decision doesn't have to be made right now, but beyond that...

Castillo is a veteran, a multi-time All-Star and a guy that the organization has trusted since acquiring him in 2022. They could leave him in the rotation when Miller comes back, likely forcing Emerson Hancock to the bullpen or to Triple-A since he has a minor league option remaining. Hancock has fared significantly better than Castillo, going 2-1 with a 2.86 ERA, but his previous bullpen experience mixed with his option present the M's with additional routes.

I've got to be honest. I'm completely against this option, at least for a while. Castillo has made 248 career appearances in the regular season and all of them are as a starter. Does he even have a routine for the bullpen? Will he be able to throw multiple times per week, or will he throw once and then the 'pen is shorthanded the rest of the week? 

And the bullpen is completely inflexible in terms of guys with minor league options, so if that happens, the M's have no place to turn for help.

We saw Castillo throw out of the 'pen in Game 5 of the 2025 American League Division Series, and it worked, but could it work over a period of months? I have my doubts.

Just a quick PSA, the 'phantom injured list,' is illegal, but if Castillo has even a mild ailment, then the Mariners could put him on the injured list, delay any ultimate decisions about his future, and hope that he unlocks something while rehabbing. 

It's certainly an option, and one the M's might need to take if Castillo continues to struggle over these next three weeks.

Castillo is due $48 million over the next two seasons. He's not being cut. Other teams are not trading for him, at least they certainly aren't taking his money. So the Mariners will not give away a durable starting pitcher while also eating $48 million.

He's going to be on this roster. It's just a question of how it manifests itself, and that's the hard part for a team with division title goals.

We talked much more about the Castillo situation on the latest edition of the 'Refuse to Lose' podcast.

The Mariners will play the Twins again on Tuesday at 4:40 p.m. PT.

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