White Sox Make Waves by Trading for Star Pitcher Castillo

WHO:

MLB.com - Luis Castillo expressed gratitude to the Mariners organization, stating, “I always tried to be a good person to everyone on the team -- a good person and good teammate.”

MLB.com - Seranthony Domínguez is expected to be added to the active roster before Tuesday’s series opener against the Tigers.

MLB.com - Luis Castillo expressed gratitude to the Mariners organization, stating, “For me, I always tried to be a good person to everyone on the team -- a good person and good teammate.”

MLB.com - Castillo was described as a legitimate leader who went about his leadership in a more under-the-radar way.

MLB.com - The Mariners are welcoming Seranthony Domínguez, who is expected to arrive at T-Mobile Park for their upcoming series against the Tigers.

MLB.com - Luis Castillo expressed gratitude to the Mariners organization, stating, “Just thanking everybody in the organization for always treating me so well."

MLB.com - Luis Castillo was traded from the Seattle Mariners to the Chicago White Sox.

MLB.com - Seranthony Domínguez, Nolan Jones, and Boston Smith were traded from the White Sox to the Mariners.

MLB.com - The White Sox are currently the only team above .500 in the American League Central.

MLB.com - The White Sox's general manager is Chris Getz.

MLB.com - The White Sox are acquiring Luis Castillo, a 33-year-old right-handed pitcher, from the Seattle Mariners.

MLB.com - The Mariners are receiving right-hander Seranthony Domínguez, outfielder Nolan Jones, and catching prospect Boston Smith in the trade.

MLB.com - The Chicago White Sox acquired right-handed pitcher Luis Castillo from the Seattle Mariners.

MLB.com - The Mariners received right-hander Seranthony Domínguez, Minor League catcher Boston Smith, and Minor League outfielder Nolan Jones in the trade.

WHAT:

MLB.com - The Mariners received cash considerations in the trade along with Domínguez, Nolan Jones, and Boston Smith.

MLB.com - The Mariners will now truncate to a five-man rotation featuring Gilbert, Miller, Hancock, Woo, and Kirby.

MLB.com - Castillo has been traded six times in his career.

MLB.com - The Mariners are expected to truncate to a five-man rotation featuring Gilbert, Miller, Hancock, Woo, and Kirby.

MLB.com - Seranthony Domínguez is expected to arrive at T-Mobile Park for the Mariners' upcoming series against the Tigers.

MLB.com - Castillo was traded to the White Sox, marking his sixth career trade.

MLB.com - Domínguez is expected to slot into a high-leverage role in the Mariners' bullpen.

MLB.com - Castillo has a 5.06 ERA in 20 outings during the 2026 season.

MLB.com - Domínguez has a 4.10 ERA in 42 outings this season.

MLB.com - The White Sox have a 2 1/2-game lead in the AL Central.

MLB.com - The White Sox pitching has yielded three runs (two earned) on 22 hits in 39 innings since July 29.

MLB.com - Castillo has a 3-9 record with a 5.06 ERA and 86 strikeouts over 99 2/3 innings in 2026.

MLB.com - The White Sox are taking on the remainder of Castillo’s contract, which totals approximately $30 million guaranteed, including $22.75 million owed in 2027.

MLB.com - Castillo has a $25 million vesting option for 2028 if he pitches at least 180 innings in 2027.

MLB.com - Domínguez is on pace for the worst season of his career, currently walking over 14% of batters faced.

MLB.com - The White Sox are currently 58-52, maintaining a three-game lead in the AL Central over both the Twins and Guardians.

MLB.com - The White Sox pitching has been especially strong over their past 39 innings, yielding two earned runs on 22 hits.

MLB.com - Castillo has a 3-9 record with a 5.06 ERA and 86 strikeouts over 99 2/3 innings in 2026.

MLB.com - Domínguez has a 4-3 record with a 3.99 ERA, a team-high 12 saves, four holds, and 47 strikeouts over 38 1/3 innings in 43 relief appearances this season.

MLB.com - Castillo is expected to start the Tuesday opener in Boston.

MLB.com - Domínguez is on pace for the worst season of his career, currently walking over 14% of batters faced.

MLB.com - The White Sox have a 2 1/2-game lead in the AL Central.

MLB.com - The White Sox pitching has yielded three runs (two earned) on 22 hits in 39 innings since July 29.

MLB.com - Castillo last pitched on July 28 at Dodger Stadium, allowing five runs on 11 hits over five innings, with two strikeouts.

MLB.com - Since May 25, Castillo has a 3.88 ERA over 10 games.

MLB.com - Domínguez, 31, is in his eighth big league season, and has a 4.10 ERA (105 ERA+) in 42 outings.

MLB.com - The White Sox pitching has been especially strong over their past 39 innings, yielding two earned runs on 22 hits.

MLB.com - The White Sox are currently 58-52, maintaining a three-game lead in the AL Central over both the Twins and Guardians.

MLB.com - The White Sox could become the first team to reach the postseason after losing 100-plus games in each of the past two seasons and the fourth team to win 70-plus games after three seasons of 100-plus defeats.

MLB.com - Castillo has a 3-9 record with a 5.06 ERA and 86 strikeouts over 99 2/3 innings in 2026, contrasting with his previous success as a three-time All-Star, having made the Midsummer Classic as recently as 2023.

MLB.com - In 13 of his last 17 starts, Castillo allowed four runs or fewer, receiving three runs of support or less 15 times.

MLB.com - Domínguez has a 4-3 record with a 3.99 ERA, a team-high 12 saves, four holds, and 47 strikeouts over 38 1/3 innings in 43 relief appearances this season.

MLB.com - The White Sox pitching has been strong over their past 39 innings, yielding two earned runs on 22 hits.

MLB.com - The White Sox have a 3-3 record against the Yankees and Rays over the past week.

MLB.com - The White Sox are currently 58-52, maintaining a three-game lead in the AL Central over both the Twins and Guardians.

MLB.com - The White Sox are taking on the remainder of Castillo’s salary, which totals approximately $30 million guaranteed, including $22.75 million owed in 2027.

MLB.com - Castillo has a $25 million vesting option for 2028 if he pitches at least 180 innings in 2027.

MLB.com - Castillo has a 3-9 record with a 5.06 ERA and 86 strikeouts over 99 2/3 innings in 2026.

MLB.com - Domínguez has a 4-3 record with a 3.99 ERA, 12 saves, and 47 strikeouts over 38 1/3 innings in 2026.

WHERE:

MLB.com - The trade was announced in St. Petersburg, Florida.

WHEN:

MLB.com - The 2026 Trade Deadline is set for Monday at 6 p.m. ET.

WHY:

The Seattle Times - The Mariners needed to shed any of Castillo’s salary that they could, and also benefit from getting him off the roster, since he was actively hurting the team with his performance.

MLB.com - The Mariners had been operating with six healthy starters since mid-May and had made it known to other clubs that they were willing to deal from that depth to address other roster needs.

MLB.com - The Mariners aimed to shed Castillo’s salary, which totals approximately $30 million guaranteed through the end of 2027.

MLB.com - The White Sox are looking to strengthen their pitching staff and maintain their lead in the American League Central.

MLB.com - The Mariners aimed to bolster their bullpen by acquiring Domínguez.

HOW:

The New York Times - The Mariners are not sending any money on the remaining $30 million guaranteed to Castillo through next season.

MLB.com - The Mariners received cash considerations in the trade along with Domínguez, Nolan Jones, and Boston Smith.

The New York Times - The Mariners received cash considerations in the trade along with Domínguez, Nolan Jones, and Boston Smith.

MLB.com - The Mariners are not sending any money to offset the remainder of Castillo’s contract, which totals approximately $30 million guaranteed.

MLB.com - The Mariners are not sending any money to offset the remainder of what Castillo is owed on his contract.

MLB.com - The White Sox are taking on the remainder of Castillo’s salary, which totals approximately $30 million guaranteed, including $22.75 million owed in 2027.

MLB.com - The Mariners are not sending any money to offset the remainder of what Castillo is owed on his contract.

MLB.com - The White Sox are using Domínguez in lower-leverage situations after he struggled in save situations, allowing one earned run over his last 10 games covering 8 2/3 innings, striking out 11 and walking five.

MLB.com - The trade involved the White Sox sending three players to the Mariners in exchange for Castillo.

Luis Castillo has expressed his gratitude to the Mariners organization, emphasizing his commitment to being a good teammate. In a recent trade, the Mariners received cash considerations along with Seranthony Domínguez, Nolan Jones, and Boston Smith, and they are expected to add Domínguez to the active roster before the series opener against the Tigers on August 8. To adjust their lineup, the Mariners will now move to a five-man rotation featuring Gilbert, Miller, Hancock, Woo, and Kirby, while also shedding Castillo’s salary without sending any money on the remaining $30 million guaranteed to him through next season.