Sources told ESPN's Jeff Passan that the Chicago White Sox will acquire right‑handed pitcher Luis Castillo from the Seattle Mariners in exchange for reliever Seranthony Dominguez, outfielder Nolan Jones and catching prospect Boston Smith. Castillo, 33, is 3‑9 with a 5.06 ERA in 17 starts this season, giving up 107 hits in 99½ innings.

He has a career 3.65 ERA over 10 seasons, though this is his worst year. Castillo is in the fourth year of a five‑year, $108 million contract that includes a vesting option for 2028. Dominguez, 31, was 4‑3 with a 4.10 ERA and 12 saves over 42 appearances for Chicago and was signed through 2027 with a two‑year, $20 million deal.

If the White Sox can extract value from Castillo, he will slot into a rotation that has featured Anthony Kay, Eric Fedde and rookie Noah Schultz. Fedde and Schultz had strong outings against the first‑place Rays, but Schultz may be moved out of the rotation. The trade also helps the team address catching depth while the starter Kyle Teel is sidelined.

The White Sox are still pursuing additional talent before Monday’s trade deadline, with another starter or reliever on the table. The organization is also looking to replenish its catching depth while Teel is out for most of the season. With Castillo’s postseason experience—something none of Chicago’s other starters currently possess—the move could provide a veteran presence in the rotation and bullpen.