Why White Sox are trading for Mariners All-Star pitcher Luis Castillo

Why White Sox are trading for Mariners All-Star pitcher Luis Castillo originally appeared on The Sporting News.
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The Chicago White Sox are buyers at the 2026 MLB trade deadline, and they’ve just made their first move of the deadline by adding a starting pitcher.

According to ESPN’s Jeff Passan, the White Sox are acquiring Seattle Mariners All-Star right-handed starting pitcher Luis Castillo in exchange for the following players: “reliever Seranthony Dominguez, outfielder Nolan Jones, and catching prospect Boston Smith.”

Adding a starter shouldn’t come as a surprise. But why did the White Sox choose Castillo from the Mariners as their first move of the deadline? There are a few reasons for this deal.

Why White Sox are trading for Luis Castillo

The first and most simple reason is that the White Sox need to upgrade their starting rotation. As good as Sean Burke and Davis Martin are, relying on the trio of Noah Schultz, Erick Fedde, and Anthony Kay isn’t ideal.

Chicago needed to add to their rotation, and even after this Castillo trade becomes official, the White Sox could still add to their rotation.

The White Sox needed to upgrade their rotation, and Castillo is a good way of doing so. It’s also important that Castillo is a veteran starter who is under club control beyond 2026.

He’s signed through the 2027 season with a 2028 vesting option on a five-year, $108 million deal. It’s a bit expensive, but the White Sox can spend a bit of money now that they might have over free agency.

Castillo is 33 years old, and while his 5.06 ERA leaves a lot to be desired, his 4.57 FIP indicates he could be a bit better this year than his current production indicates.

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There are some valid concerns about Castillo’s production, but the upside case with him as a career 3.65 ERA pitcher is worth it for the White Sox.

This team desperately needed a new starting pitcher. Castillo, who has ample MLB experience, sporting a very impressive 2.25 ERA in the postseason, and is under club control beyond 2026, is an exciting player to acquire.

Obviously, there is some risk here considering Castillo’s -0.7 bWAR and 3-9 record with a career-low 78 ERA+. But the White Sox need to take a risk, and parting with Seranthony Dominguez, Nolan Jones, and Boston Smith isn’t too large a package for Castillo.

The White Sox traded for Castillo to address their dire rotation need. He might not have exciting numbers right now, but the upside with Castillo is still there, and is worth the risk for Chicago as they eye a path for a deep postseason run in a wide-open AL.

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