Mariners Might Shake Up Rotation With Blockbuster Trade, Per Insider

The Mariners have an important offseason ahead of them.

Jun 5, 2022; Arlington, Texas, USA; A view of a Seattle Mariners batting helmet and logo during the game between the Texas Rangers and the Seattle Mariners at Globe Life Field. Mandatory Credit: Jerome Miron-Imagn Images | Jerome Miron-Imagn Images

The Seattle Mariners' season is over after losing Game 7 of the American League Championship Series to the Toronto Blue Jays on Monday night.

They have raised the standards in the Pacific Northwest, but they have a big offseason ahead of them in terms of roster moves. Several players will hit free agency, and others may be on the way out via trade.

They might look to trade from their rotation to add a bat or two to their lineup. Daniel Kramer of MLB.com listed a few players that could be traded this offseason, and among them was right-hander Luis Castillo.

Mariners 3-Time All-Star Floated As Trade Candidate

Oct 16, 2025; Seattle, Washington, USA; Seattle Mariners pitcher Luis Castillo (58) throws in the second inning against the Toronto Blue Jays during game four of the ALCS round for the 2025 MLB playoffs at T-Mobile Park. Mandatory Credit: Kevin Ng-Imagn Images | Kevin Ng-Imagn Images

"There are at least two players worth keeping tabs on this winter who might be moved: starting pitcher Luis Castillo and left fielder Randy Arozarena," Kremer wrote.

"To be sure, the Mariners admire both players and dealing them away would force the club to back-fill their spots from outside the organization. But they are also among the club's most costly."

Castillo went 11-8 with a 3.54 ERA in 32 starts and recorded 162 strikeouts in 180 2/3 innings of work this season. The likelihood of them trading George Kirby or Logan Gilbert is very slim, as those are their top two starting pitchers.

However, Castillo only has two years left on his contract, so the Mariners could potentially look to shed some salary by getting rid of him. This would be a big trade for the Mariners, as it could potentially land them a big bat from another team.

That is something they are going to need with Josh Naylor, Jorge Polanco and Eugenio Suarez all soon to be free agents. They won't be able to keep all three and will likely have to choose between Naylor and Suarez for financial reasons.

Castillo could bring back a solid haul for them after another strong season on the mound. The offense should be prioritized, and they can afford to lose a starting pitcher. They could also trade Bryce Miller, but Castillo would probably bring back the best return.

If Castillo is dealt, then the Mariners could open up a rotation spot for Emerson Hancock or potentially scour the free agent market for a low-cost fifth starter. These are some big decisions they will have to make.

We'll see where they end up landing on some of these decisions.

More MLB: Mariners Could Cut Ties With Two-Time All-Star Via Trade: Insider