The Boston Red Sox just finished their third straight non-winning season with an 81-81 record in 2024. President of baseball operations Craig Breslow wants to add an ace to his starting rotation. Could the answer include swinging a deal with the Seattle Mariners for right-handed hurler Luis Castillo?

Boston is swimming in the deep end of free agency so far this offseason. They’re in the hunt for outfielder Juan Soto and have been linked to top free-agent hurlers Corbin Burnes and Max Fried. But if Burnes and Fried take their talents elsewhere, the Red Sox may have to acquire an ace via the trade market.

One option is Garrett Crochet since the Chicago White Sox are looking to offload him this winter. Another is Castillo, who has appeared in mock trade proposals and has a longer track record of success. What could a potential deal between Boston and Seattle look like? FanSided’s Zach Pressnell put together the following hypothetical swap:

– Red Sox receive: right-handed pitcher Luis Castillo – Mariners receive: outfielder Wilyer Abreu, infielder Chase Meidroth and outfielder Jhostynxon Garcia Abreu just won a Gold Glove and finished sixth in American League Rookie of the Year voting after posting a .781 OPS with 15 home runs and 58 RBI in 447 plate appearances. Meidroth (11th) and Garcia (12th) both rank among Boston’s top 15 prospects, according to MLB.com.

Acquiring Castillo would give the Red Sox a three-time All-Star who has started at least 25 games each season since 2021 while posting a 3.51 ERA and 1.18 WHIP. He’s also entering the third season of a five-year, $108 million extension he signed with Seattle. Castillo will earn $24.15 million annually from 2025-27 and has a $25 million vesting option available for 2028.