The question of “What’s next?” has been lingering for the Seattle Mariners since they re-signed Josh Naylor, and that was a couple of weeks ago at this point. When the next shoe drops, what are the chances it could involve the Mariners subtracting a player by trading Luis Castillo?

Maybe not great, truth be told. There hasn’t been as much buzz on Castillo this winter as there was during the 2024-25 offseason, and recent moves nixed two potential landing spots for him. The Mariners might just keep him for 2026 and take whatever innings he can give them, which is usually a lot.

And yet, Mark Feinsand of MLB.com isn’t wrong to see “La Piedra” as the Mariners’ top trade candidate. Though the 32-year-old is still eating plenty of innings, he’s posted a roughly average 104 ERA+ over the last two seasons. The Mariners stand to free up $48.3 million for the next two years if they can offload Castillo’s entire contract, which notably no longer gives him the right to block trades.

Baseball Trade Values estimates Castillo’s surplus value at negative $2.9 million, which hypothetically limits the Mariners’ options to bad contract swaps and deals for low-level prospects. Yet there are still some intriguing possibilities behind those three doors, including the three discussed below.

3 mock trade proposals for the Mariners to move Luis CastilloSan Diego Padres

The Padres have already lost Dylan Cease to free agency, and Michael King could be next. Given that Yu Darvish is also out for all of 2026 following elbow surgery, there aren’t many teams out there as badly in need of a workhorse as the Padres.

Save for maybe Jake Cronenworth, the Padres don’t have much in the way of bad contracts that the Mariners would actually want to take on. It would make more sense for them to kick in some cash to essentially buy a prospect from San Diego, and Garrett Hawkins would fit the bill as expendable for the Padres and desirable for the Mariners.

Ranked by MLB Pipeline as San Diego’s No. 19 prospect, Hawkins is a 6-foot-5, 230-pound righty reliever with a plus fastball and slider. He had a 1.50 ERA and 80 strikeouts in 60 innings at High-A and Double-A this year, and could thus be a candidate for high-leverage relief work in 2026.

Baltimore Orioles

The Orioles were in on Castillo last winter, and they might need him even more this time around. Starting pitching was a major weakness for them in 2025, and there isn’t much to see in their rotation now after Trevor Rogers and Kyle Bradish.

Otherwise, Tyler O’Neill might already be a bench jockey for them just one year after he signed a three-year, $49.5 million deal that still owes him $16.5 million for 2026 and 2027. The O’s would probably be glad to rid themselves of those commitments if it meant getting Castillo, whereas the Mariners would save money and welcome back a former prospect to throw into their right field mix.

Since O’Neill’s surplus value is deeper under water than even Castillo’s, the Mariners could insist on a deal-sweetener. To this end, Gibson is another eye-popping pitching prospect who stands at 6-foot-5, 240 pounds, with a fastball that touches the high 90s. His future may be in the bullpen, in which case he could help sooner rather than later.

New York Mets

The Mets ranked 27th in innings from their starting pitchers this year, so Castillo is precisely the kind of workhorse they need — yes, even if they would still do well to also sign someone off the free-agent market.

As for Jeff McNeil, he looked like a trade candidate even before the Mets swapped Brandon Nimmo for Marcus Semien. He’s now boxed out of his natural position at second base, and a report from Mike Puma of the New York Post that McNeil and Francisco Lindor got into it this year only adds fuel to the fire.

McNeil has $15.75 million coming his way in 2026, followed by a $15.75 million option or a $2 million buyout for 2027. Taking on those commitments would be another case of the Mariners saving money, and they’d be getting a contact-first hitter who could stabilize the top of their lineup.