The Seattle Mariners have given no public indication that they plan to shake up their roster this offseason, but one move continues to linger in the background — a potential trade involving veteran starter Luis Castillo.
Castillo, a three-time All-Star, remains a dependable, above-average arm capable of logging innings, but his contract looms large as Seattle attempts to retool for another deep postseason run. The right-hander is owed $24.2 million in each of the next two seasons, with a $25 million vesting option for 2028. For a Mariners team operating within a tighter spending structure than many fellow contenders, that figure could influence difficult decisions.
After falling just short of the World Series — blowing a late lead in Game 7 of the ALCS against the Toronto Blue Jays — Seattle enters the winter with a clear objective: strengthen the lineup and add depth without losing the core that powered their October surge. But doing that while keeping payroll in check may force the front office to consider moving one of its highest-paid players.
Castillo’s trade value remains strong. Despite no longer being viewed as a frontline ace, he’s still a durable, reliable mid-rotation starter who can deliver 180+ innings and keep a team competitive deep into games. That type of arm holds significant value in today’s pitching-thin market, where even average starters are landing multi-year deals.
For Seattle, the question becomes whether those innings are worth the price tag — or whether reallocating that salary could unlock larger roster improvements.
Trading Castillo could free over $24 million in annual payroll, enough to pursue a middle-of-the-order bat, bolster the bullpen, or add multiple role players. The Mariners have the rotation depth to survive such a move as well, with George Kirby, Logan Gilbert, Bryan Woo, Bryce Miller, and Emerson Hancock forming a strong young core.
The challenge, of course, is timing. The Mariners are built to win now, and removing a veteran arm with postseason experience isn’t without risk. But if Seattle decides a major addition is necessary to finally push past the ALCS barrier, dealing Castillo may be the clearest path to the flexibility required.
For the moment, the Mariners appear content to keep the roster largely intact. But with his combination of salary, value, and age, Castillo remains their most logical — and impactful — trade chip should they decide a bold shift is needed.
The Mariners aren’t planning to rock the boat.
But if they do, Castillo is the move that could make the biggest splash.
