For the Mariners, the trade deadline chatter keeps circling back to the same uncomfortable name: Luis Castillo.
For months, moving Castillo has looked like a clean answer to more than one problem in Seattle. It would wipe his contract off the books, and it would also open a lane for Kade Anderson in the starting rotation. But according to Ken Rosenthal and Will Sammon of The Athletic, other teams “likely are reluctant” to deal for the 33-year-old because of what’s left on that contract - $24.15 million this year and in 2027, plus a $25 million vesting option for 2028.
That report points in a different direction, with Emerson Hancock emerging as the starter most likely to go. If that happens, the Mariners would still have to decide what to do with the rest of their rotation.
They could simply leave Hancock’s spot unfilled and go with five starters, but that would mean keeping Anderson in the minors. That would be a tough sell. Keith Law of The Athletic has Anderson ranked as MLB’s No. 1 prospect, and he suggested the left-hander would already be in “27 or 28” other rotations.
Seattle could also bring Anderson up and stick with a six-man group that includes Castillo, Logan Gilbert, George Kirby, Bryan Woo and Bryce Miller. But that route comes with its own problems. It keeps the six-man setup in place rather than confronting its downsides, which include fewer turns for the best starters and not necessarily any real relief for a bullpen that would still be short one arm.
That leaves a different idea on the table: Castillo to the bullpen.
It’s not a brand-new thought. The idea was floated back in early May, when it was still just a concept. Castillo was struggling as a starter then, and his splits by times through the order and pitch count hinted that he might play up in shorter outings.
The small sample from his three relief appearances in the short-lived piggyback setup backed that up. His ERA as a reliever is 5.56, compared with 4.75 as a starter, but the other numbers are more encouraging: a lower WHIP, a higher K/9 and a lower OPS.
His fastball velocity also climbed about as much as you’d expect in the shorter role.
No one is saying Castillo would turn into Mason Miller. But there’s enough there to imagine him as a leverage reliever, which opens up a path for Seattle to address its bullpen issues without going outside the organization. In that scenario, the Mariners could lean on a converted Castillo along with healthy versions of Matt Brash, Carlos Vargas and Cooper Criswell.
That’s not the role anyone would have envisioned for a pitcher making $24.15 million. Still, if the Mariners are looking for a real change, moving Castillo to the bullpen would be one. And after the way things have gone, that alone makes it worth considering.
In Other News...
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The bigger news around him, though, was the surprise change on the coaching staff. Seattle relieved assistant hitting coach Bobby Magallanes of his duties during Thursdays off-day, a move Rodrguez said caught him off guard, and he made clear how much he valued Magallanes as both a coach and a friend. For a lineup trying to stay steady in a close pennant chase, it was another reminder that the Mariners are balancing on-field urgency with some unexpected turnover behind the scenes. [Read more 🡒]
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The Mariners search for bullpen help has run into a familiar problem: the kind of arm they want is exactly the kind of arm other clubs do not give away cheaply. Padres closer Mason Miller fits the bill as a high-end late-inning option, and his club control through 2029 only adds to the appeal, but Seattles path to even getting in the conversation looks narrow with so much of its pitching core effectively off the table.
What makes the fit tricky is that a deal for Miller would almost certainly have to be built around significant talent, and the Mariners do not appear eager to part with the young starters that anchor their future. They may be more willing to discuss Luis Castillo or Emerson Hancock, but even that may not be enough to bridge the gap, leaving Seattle to weigh whether the price of chasing a premium closer is simply too steep for a club trying to stay balanced for now. [Read more 🡒]
Former Mariners Prospect Is Becoming A Painful Reminder In Arizona
Tyler Locklear is starting to look like the kind of bat the Mariners could use right now, which is exactly why his early run in Arizona lands with a little extra sting in Seattle. Traded to the Diamondbacks in July 2025, the former Mariners prospect spent the start of the 2026 season on the injured list before getting himself back on track in Triple-A Reno and earning a promotion.
Since arriving in the majors, Locklear has looked ready for the moment, and Diamondbacks manager Torey Lovullo has noticed the way he has handled the transition. After a recent game in which Locklear delivered three hits and drove in three runs, Arizona has every reason to keep leaning on him, while Mariners fans are left to wonder what might have been if that right-handed power had stayed in the organization. [Read more 🡒]