Both Randy Arozarena and Luis Castillo are candidates to be traded this winter, according to a recent list of possible offseason trade candidates from MLBTradeRumors.

Arozarena checked in at No. 22 on the 40-player list, while Castillo was No. 38.

These developments are not surprising to Mariners fans who recognize that both players are aging, and expensive, however, a trade of either player is not necessarily a definite.

On the Arozarena front

On one hand? Arozarena had an incredible season. While he only hit .238, he had an OPS+ of 119, delivering 27 home runs and 31 stolen bases. Those kind of seasons don't grow on trees and if the Mariners were to move him, they'd have to understand that's incredibly difficult to replace. 

He also had 76 RBIs and a .760 OPS. His outfield defense was suitable, though there were multiple lapses in the team's playoff run.

On the other side? He hit only .238, and he struck out 191 times, by far the highest total of his career. Predicted to make $18 or so million in arbitration, that money could potentially be more useful elsewhere.

Arozarena, 31 in February, hit .238/.334/.426 with 27 homers and 31 steals this past season. His 26.9% strikeout rate was his highest since 2021, though, and his 9% walk rate was his lowest since 2022. He posted tantalizing batted-ball metrics (91.3 mph average exit velo, 11.5% barrel rate, 50.6% hard-hit rate) but also wilted in the final two months of regular-season play (.216/.299/.343, 89 wRC+) and in the postseason (.188/.304/271 in 56 plate appearances).

Finally, if Seattle were to move him, they'd have to understand that they wouldn't be freeing up a full $18 million in payroll. They'd either be taking a player with a salary back, or they'd be keeping some portion of Arozarena's salary on the books.

The Mariners do have young outfielders working through the system (Laz Montes, Jonny Farmelo), but none of them are ready to contribute in early 2026. 

On the Castillo front

Castillo, about to be 33, lived up to his nickname "The Rock," in 2025. He was consistent, making 32 starts and working to a 3.54 ERA. And given that the M's lost Bryce Miller, George Kirby, Bryan Woo and Logan Gilbert to injuries for a portion of the season, that consistency was very important. 

However, the metrics under the hood certainly have some cause for concern:

Castillo started 30-plus games and posted a mid-3.00s ERA (3.54) for a third straight season in 2025. But the 2025 season also marked three consecutive years of declining velocity and two consecutive years with a lowered strikeout rate. Castillo also surrendered career-worst marks in opponents’ average exit velocity, barrel rate and hard-hit rate. He’ll turn 33 in December. He’s not a massive, obvious regression candidate, but there are some red flags to consider.

If the Mariners were to trade him, they'd be losing out on that consistency, which is a very big deal for any rotation. And similar to Arozarena, they won't be freeing up the full $24-ish million or so in payroll, so it may not be worth it to deal him without significant salary relief.

However, if they were interested in back-filling the rotation with a veteran arm on a short-term deal, there will be opportunities to do that.

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