The Seattle Mariners acquired right‑handed reliever Seranthony Domínguez, minor‑league catcher Boston Smith, minor‑league outfielder Nolan Jones, and cash considerations from the Chicago White Sox in a trade that sends veteran starter Luis Castillo to Chicago, the club announced Sunday.
President of Baseball Operations Jerry Dipoto acknowledged the significance of parting with Castillo, who has been central to Seattle’s recent postseason runs.
“‘The Rock’ has been an integral part of this era of our organization’s history,” Dipoto said. “His arrival and performance in 2022 set the tone for what has been a fantastic run as a Mariner. We appreciate everything he has done in Seattle and wish him continued success.”
Domínguez Adds Late‑Inning Experience and Strikeout Stuff
Domínguez, 31, has been a key bullpen arm for Chicago this season, posting a 4–3 record, 12 saves, and a 4.10 ERA across 42 appearances. His 10.85 strikeouts per nine innings ranks 15th among American League relievers with at least 30 innings pitched. Signed through 2027, Domínguez brings eight seasons of Major League experience with Philadelphia, Baltimore, Toronto, and Chicago.
Across his career, the Dominican Republic native owns a 19–17 record, 52 saves, and a 3.57 ERA with 405 strikeouts in 343.1 innings.
Smith Arrives as a Fast‑Rising Catching Prospect
Smith, 23, has been one of the White Sox system’s breakout performers in 2026. Across three levels, he is batting .291 with 22 home runs, 58 RBI, 74 walks, and a 1.037 OPS in 78 games. MLB Pipeline ranks him as the No. 15 prospect in Chicago’s organization.
A sixth‑round pick by Washington in 2025, Smith was traded to the White Sox earlier this year and made his professional debut in 2026.
Jones Provides Versatility and Power from Triple‑A
Jones, 28, has hit .257 with 14 home runs, 59 RBI, and an .807 OPS in 90 Triple‑A games split between the White Sox and Guardians organizations this season. He has appeared in parts of four Major League seasons, highlighted by a 20‑home run, 20‑steal rookie campaign with Colorado in 2023 that earned him a fourth‑place finish in NL Rookie of the Year voting.
Castillo Heads to Chicago After Five Seasons in Seattle
Castillo, 33, departs Seattle after a challenging 2026 season in which he posted a 3–9 record and 5.06 ERA across 20 appearances. Since joining the Mariners in 2022, he has been a cornerstone of the rotation, going 43–40 with a 3.69 ERA in 126 games and contributing to postseason runs in 2022 and 2025.
Over his 10‑year Major League career with Cincinnati and Seattle, Castillo owns an 87–93 record, 3.65 ERA, and 1,579 strikeouts across 1,510.1 innings.
The trade marks a significant shift for Seattle, adding bullpen depth and two controllable position‑player prospects while closing the chapter on Castillo’s tenure as the club’s ace.
