The Seattle Mariners parted ways with one of their longest-tenured players on Saturday night, sending right-hander Luis Castillo to the Chicago White Sox in exchange for right-hander Seranthony Domínguez, outfielder Nolan Jones, catching prospect Boston Smith, and cash considerations. The struggling Mariners entered the deal four games below .500 and trailing the Houston Astros by three games in the AL West, prompting a major roster shakeup ahead of the trade deadline.
Luis Castillo Traded to the Chicago White Sox
Castillo, 33, is under contract through the 2027 season with a vesting option for 2028. He compiled a 3-9 record with 86 strikeouts and a 5.06 ERA across 99 2/3 innings this season. Meanwhile, the White Sox arrived at the deal leading the AL Central by 2 1/2 games with a 58-52 record.
Return Package Brings Pitching and Prospect Depth
In return for Castillo, Seattle acquired a mix of major league experience and minor league upside. Domínguez, 31, holds a 4-3 record with a 4.10 ERA across 42 games this season. Jones, 28, split his time between Triple-A Charlotte and Triple-A Columbus—the top affiliate for the Cleveland Guardians—without appearing in a major league game for Chicago this year.
The package also features catching prospect Boston Smith. The 23-year-old is hitting .291 with 22 home runs and 58 RBIs across stints at three minor league levels. The Washington Nationals selected Smith in the sixth round of the 2025 MLB draft before trading him to Chicago in March for utility man Curtis Mead.
Rotation Surplus and Emerson Hancock Trade Odds
Despite parting with Castillo, the Mariners maintain a deep surplus of starting pitching options. Earlier in the 2026 season, manager Dan Wilson paired Castillo and right-hander Bryce Miller in a piggyback setup to ensure Seattle’s six starting pitchers could all regularly appear in games. Without Castillo, the Mariners’ rotation depth still features Miller, former first-round pick Emerson Hancock, George Kirby, and former All-Stars Logan Gilbert and Bryan Woo.
Trade deadline attention has also centered on Hancock. According to ESPN’s Jeff Passan and Kiley McDaniel, Hancock carries a coin-flip chance of being dealt before the deadline.
Passan and McDaniel write that the team’s dreadful start to the second half altered their calculus regarding their starting pitching surplus. Hancock, a 27-year-old right-handed starter, has posted a 3.26 ERA in 20 starts with 2.5 bWAR and remains under club control until after the 2030 season.“Chance of being traded: 50%,”
Jeff Passan and Kiley McDaniel, via Sporting News
Bryan Woo’s Health and Bryce Miller’s Bullpen Outing
Bryan Woo made his first start since experiencing right shoulder discomfort on Aug. 14 in Houston, lasting just four innings and 76 pitches while surrendering all six runs—including home runs to Bryce Harper and Kyle Schwarber. Woo insisted the abbreviated outing stemmed from the damage against him rather than lingering physical effects.
Bryan Woo, via MLB.com
Woo also dismissed any impact from a long layoff, stating, I don’t think at all.
Ahead of the game, right-hander Bryce Miller prepared as a just-in-case arm out of the bullpen to cover innings in case Woo experienced renewed shoulder issues. Because Wednesday marked Miller’s standard in-between throw day, the coaching staff arranged for him to join the bullpen crew during the game’s middle stages. General manager Justin Hollander noted earlier in the week that the results do matter, as do how guys are feeling,
adding that management takes all factors into account when making roster decisions.
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