LOS ANGELES, CALIFORNIA - JULY 28: Luis Castillo #58 of the Seattle Mariners pitches during the third inning against the Los Angeles Dodgers at Dodger Stadium on July 28, 2026 in Los Angeles, California. (Ross Turteltaub / Getty Images)
The Seattle Mariners have swung their first trade of deadline season.
The Seattle Mariners traded right-handed pitcher Luis Castillo to the Chicago White Sox in exchange for right-handed reliever Seranthony Domínguez, outfielder Nolan Jones, and catching prospect Boston Smith.
The Mariners also receive cash considerations from the White Sox.
The deal was first reported by Jeff Passan of ESPN.com.
"’The Rock’ has been an integral part of this era of our organization’s history," president of baseball operations Jerry Dipoto said in a statement. "His arrival, and subsequent performance in 2022 set the tone for what has been a fantastic run as a Mariner. We all appreciate everything he has done in Seattle and wish him continued success in all he does."
The Mariners have been blessed with too many solid starting pitchers, with the emergence of Emerson Hancock this year forcing the team into using a six-man rotation at times. Castillo, 33, has been the least successful of the group this season and is the oldest of the bunch. Castillo is 3-9 with a 5.06 ERA over 99 ⅔ innings pitched this season with 32 walks and 86 strikeouts.
Multiple reports have stated that the Mariners aren't responsible for any of the remaining money on Castillo's contract. Castillo is signed through 2027 with a $25 million vesting option for 2028. He is earning $22.75 million this year and next on his contract with the White Sox responsible for around $7 million for the rest of this year.
A key trade deadline acquisition by the Mariners in 2022, Castillo has been a standout during his five seasons in Seattle. Castillo leaves the Mariners with a career 43-40 record with a 3.69 ERA over 126 appearances and 123 starts. He was an All-Star pick in 2023 and finished fifth in AL Cy Young voting.
Domínguez, 31, is the primary acquisition of the deal for Seattle. Domínguez has appeared in 42 games this season with Chicago, holding opponents to a .206 batting average against with a 4.10 ERA in 37 ⅓ innings pitched, along with 23 walks and 45 strikeouts.
Domínguez was a key part of the bullpen for the Toronto Blue Jays in last year's ALCS against the Mariners. He made 12 postseason appearances for the Blue Jays, pitching 11 ⅓ innings with four runs allowed for a 3.18 ERA. The Mariners were responsible for three of the four runs he allowed in the playoffs, including Eugenio Suárez's grand slam in Game 5.
Domínguez is signed through the 2027 season with a mutual option for 2028. He's scheduled to earn $10 million next year, with a $12 million option that carries a $2 million buyout in 2028. He'll earn a prorated $7 million, which is a little over $2 million, for the rest of the year with Seattle.
Jones, 28, has appeared in 349 career MLB games with the Cleveland Guardians and Colorado Rockies, but has not played in the majors this season. In 90 games split between Triple-A Columbus (CLE) and Charlotte (CWS), Jones has hit .257 with 16 doubles, a triple, 14 home runs and 59 RBI with 53 walks and 95 strikeouts.
Jones also bats left-handed, which the Mariners have a surplus of as well.
Smith, 23, was a sixth-round pick of the Washington Nationals in the 2025 MLB Draft and has played in 78 games between A-ball and double-A in the White Sox system this season. Combined, he's hit. 291 with seven doubles, three triples and 22 home runs for 58 RBI with 74 walks and 96 strikeouts. In 22 games with Double-A Birmingham, Smith has hit .306 with two doubles, eight home runs and a 1.146 OPS.
The Source: Information in this story came from ESPN.com, the Seattle Mariners and FOX 13 Seattle reporting.
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