The Seattle Mariners traded veteran right-handed pitcher Luis Castillo to the Chicago White Sox in exchange for right-hander Seranthony Domínguez, outfielder Nolan Jones, catching prospect Boston Smith, and cash considerations, according to the messenger-inquirer.com. The deal was announced Saturday night ahead of Monday’s trade deadline.
Mariners Trade Luis Castillo to Chicago White Sox
Castillo, 33, is enduring the worst statistical season of his career, posting a 3-9 record with a 5.06 ERA across 20 appearances and 17 starts, allowing 107 hits in 99 1/2 innings. As part of the agreement, the White Sox will absorb the remainder of Castillo’s contract, which includes approximately $7.4 million left on his 2026 salary, more than $24 million for 2027, and a $25 million vesting option for 2028 that triggers if he logs 180 innings next season and enters the following year healthy, according to MLB Trade Rumors.
Financial Terms and Contract Details
The transaction features significant financial maneuvering for both franchises. The White Sox take on the entirety of Castillo’s lucrative deal, which is in the fourth year of a five-year, $108 million extension he signed after being acquired by Seattle from Cincinnati four years ago. That historic 2022 deadline acquisition helped the Mariners end a 21-year playoff drought.
To help offset the massive salary intake, the White Sox are sending Domínguez to Seattle. Domínguez is signed through 2027 under a two-year, $20 million contract inked prior to the season, leaving about $15.2 million remaining in total obligations, which includes $3.2 million in 2026 salary, $10 million for 2027, and a $2 million buyout for a 2028 mutual option, as reported by MLB Trade Rumors.
Return Package Heading to Seattle
The return package brings three distinct pieces to the Seattletimes organization:
- Seranthony Domínguez: A 31-year-old reliever who went 4-3 with a 4.10 ERA and 12 saves across 42 appearances for Chicago this season. He will slot into a high-leverage bullpen role behind closer Andrés Muñoz.
- Nolan Jones: A 28-year-old left-handed-hitting outfielder who finished fourth in NL Rookie of the Year voting with Colorado in 2023 after hitting 20 home runs with 20 steals, though he spent this season entirely in Triple-A.
- Boston Smith: A 23-year-old catching and outfield prospect ranked No. 15 in the White Sox system by MLB Pipeline, who batted .306 in 22 games at Double-A this year after being acquired from the Washington Nationals.
Roster Impact and Future Outlook
For Chicago, the acquisition addresses an urgent need for starting pitching depth as the club maintains a lead in the AL Central and pushes toward the postseason. Castillo joins a middle of the rotation that has featured Davis Martin, Sean Burke, Anthony Kay, Erick Fedde, and rookie Noah Schultz, bringing essential postseason experience to a young pitching staff.
For Seattle, trading Castillo alleviates a rotation surplus that earlier in the season required manager Dan Wilson to use a “piggyback” system pairing Castillo with Bryce Miller. Seattletimes reported that the Mariners may continue engaging suitors regarding other rotation members and pending free agents ahead of the trade deadline.
