It's been no secret that the Chicago White Sox have needed a starting pitcher. They were rumored to be in on several, but they finally got their guy.According to ESPN's Jeff Passan, the White Sox have acquired Seattle Mariners starter Luis Castillo in exchange for reliever Seranthony Dominguez, catching prospect Boston Smith, and outfielder Nolan Jones.Instant Grade on Luis Castillo TradeJul 3, 2026; Seattle, Washington, USA; aSeattle Mariners starting pitcher Luis Castillo (58) walks off the field during a game against the Toronto Blue Jays t T-Mobile Park. Mandatory Credit: Stephen Brashear-Imagn Images | IMAGN IMAGES via Reuters ConnectLuis Castillo is an experienced arm who can potentially help the White Sox in the postseason. In six career playoff games (five starts), Castillo has a 2.25 ERA. However, he's having a very rough season. The three-time All-Star has a 5.06 ERA in 20 games (17 starts) thus far. This was after a 2025 season where he had a 3.54 ERA in 32 starts.Castillo is in his age-33 season and has control through the 2027 season with a five-year, $108 million deal, with a vesting option for 2028 that is unlikely to be picked up. The White Sox will reportedly pick up all of his remaining salary ($22.75 million this year and next year). Picking up a veteran with playoff experience was paramount for the White Sox at this deadline. But to absorb that salary for a pitcher having a horrible season is questionable at best. Let's now look at what general manager Chris Getz gave up ...Overall, Seranthony Dominguez was having a rough season (12 of 17 on save opportunities), especially after the high expectations that came with his two-year, $20 million free agent contract. But lately, he seemed to be figuring it out. In his last seven games, he had a 1.59 ERA. However, in all fairness, the emergence of fellow reliever Grant Taylor made Dominguez expendable.Nolan Jones was a former top prospect of the Colorado Rockies who was acquired by Chicago this year and stashed in Triple-A. In Charlotte, he had a .752 OPS and was likely a throw-in for the trade.But the piece of the trade that makes this a potential overpay hasn't made it to Charlotte yet. Smith was the No. 15 prospect in the White Sox system and rising, and practically the only young catcher in the system with a positive trajectory in the organization. Between Low-A, High-A, and Double-A, Smith has had a .291/.448/.589 slash line with 22 home runs and flashed solid defense and athleticism. The White Sox acquired Smith in their trade with the Nationals for Curtis Mead in March. There is no question that Smith has since exceeded expectations, and there is a world where the White Sox are selling high on his 2026 output. But, still, he was playing good enough baseball that giving up feels a tad concerning. Indeed, forking over a promising prospect like that points to how Getz is going to approach this deadline. Since Smith is gone, few might be truly untouchable in the White Sox organization. Getz seems to be going for it all at the deadline, instead of practicing patience in what was supposed to be a rebuild year.White Sox Grade: CThe Mariners may have made out like bandits in this trade, shedding a suddenly unwanted contract for a ton of potential. The White Sox gave up a rock-solid prospect and an improving reliever for a player who has underperformed. Enough said. This likely won't be the last trade Getz makes before the deadline, however, so fasten your seatbelts, folks!Add us as a preferred source on GoogleFollow