The White Sox have made their first notable move ahead of the deadline.
The team is acquiring right-hander Luis Castillo in exchange for reliever Seranthony Domínguez, outfielder Nolan Jones, and catcher Boston Smith. The news was first reported by ESPN’s Jeff Passan and made official later Saturday night.
As part of this move, the White Sox will reportedly absorb all remaining money on Castillo’s contract, per ESPN’s Alden Gonzalez. That includes the pro-rated portion of $22.75 million for this year and $22.75 million next year. Castillo’s deal also has a $25 million vesting option for 2028 if he reaches 180 innings, which seems rather unlikely at this point.
Castillo has struggled this season with Seattle. Across 99.2 innings, the right-hander has a 5.06 ERA and a 1.395 WHIP. It’s a far cry from the mid-3 ERAs and 1.1 WHIPs he posted in each of his first three full seasons with the Mariners. Castillo’s strikeout rate has also plummeted this season, falling from 9.0 K/9 in 2024 to 8.1 in 2025 to 7.8 this year.
After a strong June, hitters roughed up the veteran to the tune of a 5.48 ERA across four starts in July. One area that the Sox will look for improvement in is Castillo’s ability to manage the long ball. Of the 16 home runs that Castillo has surrendered this season, seven have come across his last three starts.
Despite all of his struggles, Castillo has managed quality starts in three of his last five appearances. His ability to pitch deep into games was certainly appealing to a Sox team that has gotten a league-worst 478.2 innings out of its starting rotation this year (though the team’s dependency on openers skews that number).
Also of interest to the Sox is Castillo’s postseason success. He owns a 2.25 ERA in 28.0 career postseason innings, most recently blanking the Detroit Tigers in Game 2 of the 2025 ALDS. He also shut down the Tigers during a scoreless relief appearance in Game 5 of the same series.
Castillo’s fit with the Sox is much clearer than with the Mariners, where he sometimes appeared in relief as the team juggled six starters. What’s more murky is who gets bumped from the Sox rotation to accommodate the veteran.
Noah Schultz, despite a strong appearance against the Rays on Saturday, seems to be the most likely candidate. Erick Fedde, however, could also lose his spot and transition into a Castillo-like piggyback option.
Because of Domínguez’s inclusion in the deal, the Sox don’t have to send anyone down to add Castillo to the roster, but if they optioned Schultz to Charlotte, for example, someone like Hagen Smith or Tanner McDougal — who have both been working as relievers as of late — could take the open spot in the bullpen.
Domínguez’s inclusion also helps lighten the burden of Castillo’s massive salary. While the Sox will be paying Castillo’s contract in full for the rest of this season and all of next season (well, as much of next season as actually takes place), they’re moving the $10 million owed to Domínguez in 2027 off the books.
The big get for Seattle is catcher Boston Smith, who owns a 1.037 OPS across three levels this season. The bespectacled backstop has 22 home runs in 78 games, eight of which have come in his 22 games with the Barons. The Sox acquired Smith from the Washington Nationals in exchange for Curtis Mead earlier this year.
It’s a tough loss for a farm system thin on quality sluggers, but also an apparent vote of confidence in Kyle Teel, though further moves may be coming. For all of his success, Smith is likely some time away from the majors, as 2026 was his first taste of professional baseball.
The trade’s final piece — outfielder Nolan Jones — strung together 39 serviceable games with the Knights after joining the organization in mid-June.
While the move is certainly a splash, the Sox still have several areas of need, and with a day and a half until the deadline, could continue to stay busy.
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