The Boston Red Sox and Seattle Mariners have been surrounded by trade rumors since Winter Meetings.
MLB Network insider Jon Morosi and reporters Ryan Divish and Adam Jude from The Seattle Times have been the sources of many of the speculations, but there have also been some real moves attempted between the two sides. Boston tried to trade Triston Casas to Seattle in exchange for one of its young starters, Bryan Woo or Bryce Miller, but the M's have been wholly uninterested in dealing from their group of rotation arms.
This is great news for the swath of Red Sox fans who don't want to see Casas traded, but the rumors haven't ceased. It is most often speculated that the Sox hope to trade for veteran righty Luis Castillo with Casas as the Mariners' return, or part of it. MLB insiders Jim Bowden and Mark Feinsand have posited such a trade as recently as Dec. 17.
Yet, Alex Speier of The Boston Globe has repeatedly shut down any rumors of a Casas-Castillo trade. Speier first refuted the rumors during Winter Meetings, and he doubled down on his reporting in the Dec. 17 installment of NESN's "310 to Left" podcast.
Red Sox reporter shuts down more Triston Casas for Luis Castillo trade rumors
"That's not what Seattle would be interested in as a potential package. . . and, I should also step back, the Red Sox wouldn't have a ton of interest in a Castillo for Casas deal either," Speier said. "The reason being if they did that, then all of a sudden, you're taking on [Castillo,] who's been an All-Star-caliber pitcher in multiple years of his career, but had a down year last year, and you do start to worry about whether or not the mileage is going to be taking him in that direction."
Speier also mentioned Castillo's drastic home/road splits as a deterrent for a potential trade. Seattle's home field, T-Mobile Park, is notoriously pitcher-friendly, and each of the Mariners' starters benefit greatly from playing half their games there. Castillo pitched to a 3.15 ERA in 97 innings at home in 2024 and a 4.25 ERA in 78.1 frames on the road.
The Mariners are more interested in shoring up other infield spots, and the Red Sox have concerns about the amount of money and risk they'd take on if they traded for Castillo. That doesn't mean a trade involving other players won't happen between the two organizations, but Casas for Castillo seems to be off the table for both parties here.