Padres could target Mariners veteran starter in speculative winter trade

The San Diego Padres will need rotation help in 2026. They are set to lose Dylan Cease and Michael King in free agency, leaving them with just four projected starters on the roster next year. That includes the veteran Yu Darvish, coming off arguably the worst year of his career, and Joe Musgrove, who has not pitched in over a year.

Obviously, there is a need to be filled, and while the Padres could look for cheaper options, there is a good chance one of the most consistent starters in the league will be available on the trade block this winter. Should the San Diego Padres consider trading with the Seattle Mariners for Luis Castillo?

Mariners ace Luis Castillo pops as a realistic Padres trade fit

AJ Preller and Jerry Dipoto have a history of making deals together, most notably in 2020, in a seven-player trade that sent Ty France, Andrés Muñoz, Taylor Trammell, and Luis Torrens to Seattle in exchange for Austin Nola, Dan Altavilla, and Austin Adams.

It would not be hard to see a Castillo trade happening for the Mariners. Seattle will likely be looking to cut costs, with younger stars like Cal Raleigh, Julio Rodriguez, Randy Arozarena and Logan Gilbert projected to earn big raises in 2026. Castillo, while dominant, is costly, owed $24 million a year for the next two years.

The Padres tend to be more willing to spend, especially for guys like Castillo, who have proven value. The nice thing about Castillo's contract is that it's just a two-year commitment (with a vesting option in 2028). If he struggles, it cannot hurt San Diego long-term, a big thing that would make Castillo a different case than the contracts handed out to Xander Bogaerts and Manny Machado.

And what are the chances that Castillo struggles? Probably pretty low, considering his recent track record. Since 2018, Castillo has not posted an ERA above 4, and has missed just 12 starts over the past seven years. He's durable, and he's consistent. In his career, Castillo has a 3.55 ERA, a 3.73 FIP, and a 118 ERA+. He's a three-time All-Star and finished fifth in Cy-Young voting in 2023.

Ultimately, a Castillo trade would probably come down to three questions. How much are the Padres willing to spend on their rotation? Will they bring back either King or Cease? What would San Diego be willing to give up to get Castillo?

There is definitely a world where a trade like this could happen, but until we know the answers to those questions, it is hard to predict the likelihood. Still, it would be fun to watch Castillo as a Padre.