A Red Sox-Mariners trade could be a winning backup plan for Boston.

The Boston Red Sox have been looking for an ace all offseason. They were linked to left-handed ace Blake Snell before Snell signed a massive five-year contract with the Los Angeles Dodgers. Boston has also been linked to pitchers such as Jack Flaherty, Corbin Burns, Max Fried and other top free agents. Outside of free agents, Boston is rumored to be among the top trade candidates such as Sonny Gray or Garrett Crochet.

The most likely scenario sees Boston adding two starters to the roster this winter. One of the pitchers listed above and one unexpected mystery hand.

The surprise hand could very well come from the Seattle Mariners, who have plenty of talented pitchers with a lackluster roster. If the Mariners want to move a pitcher, Luis Castillo will undoubtedly be the most sought after player.

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Castillo is under contract until 2027 with a transfer option in 2028. His contract is a decent size, so Seattle would likely have to pay a small portion of the deal to move Castillo. Boston could be one of the teams that could implement this idea.

In this deal, the Mariners are expected to pay about a third of Castillo’s remaining contract. Because of this, Seattle will receive some pretty solid revenue.

Villier Abreu is rumored to be someone Boston is looking to move this winter. Abreu, 25, posted 3.5 WAR while hitting .253/.322/.459 and earning a Gold Glove in the outfield. He’s an incredibly valuable asset for Boston, so sending him to Seattle won’t be easy. Given that the Mariners have a talented outfielder, they aren’t looking for a regular outfielder, but Abreu is too talented to pass up.

Meidroth, 23, hit .293/.437/.400 at the Triple-A level in 2024. He has a natural ability to reach base while hitting nearly .300. The Mariners need infielders, and Meidroth is an MLB-ready infielder who could make a difference this season.

Garcia, 21, hit .286/.356/.536 while rising through the minor leagues last season. He is a deep power threat with a growing ability to put the ball in play and get on base.

Castillo has been Bonafide’s ace for quite some time. Over the past five seasons, he has been among the league’s best pitchers, consistently posting an ERA below 4.00. He would be a huge addition to the Red Sox rotation, especially if Boston can add an arm like Max Fried next to him at the top of the staff.