Sooo, about this Luís Castillo trade talk

Will they? Won't they? We'll hit both sides.

For anyone who writes a blog or is considering writing a blog or newsletter or whatever, let me clue you in on a little secret. This is advice I give professionally so you know it’s good. It is waaaaay easier to write about something that’s happening and people are actively conversing on than an idea completely from your own head.

I started something of a trade target primer two weeks ago and that’s why there haven’t been any posts since. It’s not done and grows increasingly irrelevant by the day. How fun.

So let’s instead talk about something people have been talking about, and try to do so in an efficient number of words.

Should the Mariners trade Luís Castillo? Should they not? Let’s hit both sides of it.

It might be smart to cash in on Castillo’s value now

Here’s the deal. Let’s say the Mariners had, if not unlimited money, then something like a $200 million payroll. Or, any somewhat-believable figure.

Here’s the cold-blooded question: is 2025 Luís Castillo the best way the club can spend $22.75 million? Is he the best way they can spend approximately $68 million over the coming three seasons?

There’s room for debate.

For one, Castillo was the Mariners’ fourth-best starter in 2024, tied with Bryan Woo at 2.3 fWAR in approximately 50 fewer innings than the young righty. Across baseball, this put him/them around names like Andrew Heaney, Jameson Taillon, Zack Littell and Luis Severino.

Severino, of course, just signed for…almost exactly what Castillo is owed over the coming three seasons, at $67 million. So the value is there. This isn’t some albatross contract the Mariners are looking to get out from under. He should return value.

Another big question: is this the last window to move Castillo, with his full contract, and get real value back?

This is a bit of anecdotal data, but it’s data nonetheless—here’s Castillo’s average velocity on his two fastballs over the prior four campaigns.

Note the heavily (albeit automatically) elevated Y-axis here. It’s not as steep a decline as it shows. But we are talking about dropping close to two full ticks on the four-seamer since he joined the Mariners.

How’s that working for him? Could be better.

When looking at rolling 10-game samples for three important metrics—strikeout percentage, swinging strike rate and chase rate—we saw a noticeable dip midway through last season.

FanGraphs’ depth charts have Castillo bouncing back to 2.8 fWAR in 2025, good for the 39th-best starter in their projections. It’s a skosh below Nathan Eovaldi, who at 34 (two years older than Castillo), will make $75 million over the next three years after inking a new deal with the Texas Rangers.

It’s more than reasonable to think Castillo would make more than what he’s owed were he on the open market. As such, the Mariners are right to ask for more than salary relief. Probably a good deal more.

But, should they need or want to move on from him a year from now instead, will that still be the case? What if the velo and value continue to dip? What if he gets hurt?

If the Mariners can fill a need—or two?—with Castillo while freeing up money for Christian Walker, is that something they should consider? It’s tough to argue it isn’t.

We’ll do it, though.

Trading Luís Castillo would be a giant bummer and continue to cement the Mariners as a second- or third-rate franchise

This part of the exercise is probably going to be a good deal less objective and data-based. Is it any more wrong? That’s up to you.

I’ll start by putting it like this: trading Luís Castillo in the middle of a contention window is not what a world-class organization would do. Not at all.

You got this guy to get you into the dance, he did. You got this guy to win you the big game, he did. When he starts to slide a little, you have his back and let him age into the back-half of the rotation but still win you a playoff game or four.

What message would trading him send to other elite players around the league? What message it would it send to elite players in your own clubhouse?

Should certain conditions be met, you’re gone. The biggest one: you make more money than they’d like you to make. Even if they just signed up to give you that money.

Logan Gilbert and George Kirby have heard their names kicked around. Cal Raleigh has to figure he’ll see his soon. How long before “they’re not hanging up” on calls about Julio?

Maybe this is too pie-in-the-sky but running what could be a golden era in Mariners baseball like it were the Ship of Theseus isn’t the only way to do it.

Who’s going to want to sign an extension, sign up to be in this for the long haul when the organization has shown words are just words? Or sign as a free agent and put down roots when yours can be yanked as easily as anyone’s?

That’s before get to the more logic-based side of this.

This is really shallow and borders on patronizing but is important to state: if you trade away a positive contributor, your only gain on the move comes if the return is not only better than the outbound player(s), but notably better.

Let’s say Luis Castillo marches toward another roughly 2.5 fWAR campaign. That’s somewhere between 2017 and 2018 Mike Leake. If the Mariners want to improve by even two wins, they’ll need 4.5 2025 fWAR on the return. That is so tough.

And that’s before we get to extenuating circumstances. Castillo’s spot, in all likelihood, would not be backfilled. Even if they miraculously land Rōki Sasaki, they’d be counting on a lot of young arms to get them where they’re trying to go, two of them with ample injury baggage.

If they don’t land Sasaki, you’re one serious arm ailment—something they’ve basically walked on water to avoid thus far—from blowing a hole in the best thing they have going.

Hell, trading Castillo now would be doing exactly that.

And by “now” I mean like now, while this talk is bubbling. If you were going to move your horse, why would you do it before you know where Sasaki ends up?

To jump the Corbin Burnes market—I guess?

Have an abundance mindset, see how the Sasaki pursuit plays out and, if someone’s there to make the desperation offer you’d be willing to take, even without Saski, take it then.

Trading La Piedra now is what an unambitious second-rate team would do. It’s what a third-rate team focused on profits over everything would do.

I can’t say it’s something the Seattle Mariners as we know them now wouldn’t do.

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The big point from me in all of this, and on most things Mariners and otherwise: it doesn’t have to be like this. It is, but it doesn’t have to be.

Money gives baseball teams a margin for error. That’s why the good teams usually have and use it.

Maybe Luís Castillo and his contract aren’t a good value over the coming three springs, summers and, hopefully, autumns.

But maybe baseball’s about more than that.

I hope so, at least.