Red Sox are closest thing to favorites for Luis Castillo, but it comes with a catch

About 2.5 years ago, the Seattle Mariners acquired starting pitcher Luis Castillo from the Cincinnati Reds for a package of prospects highlighted by Noelvi Marte, who was the Mariners' top prospect.

Now, as we near 2025, the Boston Red Sox are interested in acquiring Castillo from the Mariners... but it might cost them a top prospect. While the Mariners reportedly want an immediate impact bat — Triston Casas is the most popular name thrown out in a potential Castillo trade — that deal doesn't appear to have much traction.

Instead, the Mariners could pivot what they're asking for in return. According to Mark Sheldon at MLB.com, "Seattle could look to trade Castillo for an impact bat, though it’s possible the Mariners could try to offload his salary with the idea of improving the lineup via free agency," which frankly sounds like yet another money-saving move from Mariners owner and notoriously cheap human John Stanton. You'd think having 1.1 billion dollars wouldn't require any "cost-saving measures, but you'd be wrong, apparently.

That's not Boston's problem, though. What is potentially Boston's problem is that, should Seattle decide to "unload" Castillo, it would be in the form of prospects. Also from Sheldon, "Seattle could also move Castillo for prospects, then use the money it had earmarked for the pitcher to sign a free agent such as Christian Walker."

Again, the Seattle Mariners aren't likely to sign Christian Walker because the front office does not care about its fans (no I'm not bitter, why do you ask) but if that's the direction this potential trade goes, would the Sox be willing to part with a top prospect for Castillo?

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Boston has four MLB Top 100 prospects

Roman Anthony, Marcelo Mayer, Kristian Campbell and Franklin Arias are Boston' top four prospects, and each of them are in the MLB's top 100 prospect rankings — Anthony, Mayer and Campbell are all in the top 10.

Would Boston be willing to part with any of those players in a Castillo deal? Would they be more willing to do that instead of giving up Casas, who's already proved to be an MLB-level bat? I'm not sure. Realistically, the Red Sox would probably scoff at a Mariners offer that included Anthony or Mayer, but starting pitching help isn't easy to come by right now... desperate times and all that.

Maybe the Mariners are willing to throw in another MLB player to ease the blow of Boston losing a top 100 prospect. Would Castillo and, say, Ryan Bliss make parting with a prospect more stomachable?

The Red Sox are looking for direction right now; after three seasons of mediocrity, the way this front office is operating points toward a desire to win now. Luis Castillo would help them do that. But what Boston is forced to send in return might not justify the move in the first place.