At some point, every ugly Luis Castillo update stops feeling like an anomaly. This could no longer be an isolated setback. Castillo is going downhill, so much so the White Sox GM couldn’t hold back from saying it himself.

The White Sox recently moved Castillo to the bullpen after skipping one of his turns in the rotation. His first relief appearance didn’t provide the reset they expected. He allowed three earned runs and walked another three over 2 2/3  innings against the St. Louis Cardinals.

White Sox general manager Chris Getz then acknowledged the numbers.

“It’s trended in the wrong direction,” Getz told ESPN’s Jesse Rogers. “It has been surprising.”

Getz didn’t publicly declare the trade a mistake here. Not many GM’s would volunteer that kind of honesty six weeks after a deadline deal, especially with the money tied to the remaining deal. Still, when a team acquires a veteran starter for a division race and its GM is already discussing how surprisingly wrong things have gone, we don’t need a translator.

Luis Castillo’s White Sox Numbers Are Getting Difficult to Explain Away

Castillo owns a 7.76 ERA and 1.79 WHIP through seven appearances with the White Sox. He has allowed 41 hits and 25 earned runs across 29 innings while striking out 25 batters. He managed to splash in a vintage performance inside the wreckage against his former team, the Cincinnati Reds on August 12, where he threw seven scoreless innings, allowed one hit and struck out 10.

That showed why Chicago wanted him. Everything that surrounded it has shown why the Mariners were willing to let him go. This has gone beyond a starter struggling to adjust after a trade. The White Sox acquired Castillo to stabilize their rotation during a playoff race. Barely a month later, they were trying to determine whether he could help them as a reliever.

That’s a sharp and uncomfortable turn. It’s also the kind of turn Seattle spent months avoiding. The White Sox watched Castillo struggle and didn’t hesitate to send him to the bullpen. No six-man rotation. No prolonged piggyback arrangement. Chicago made the uncomfortable decision its situation demanded.

Even the White Sox were willing to go where the Mariners refused to go. The M’s spent the early summer trying to solve its crowded rotation without bruising anyone’s ego. The Mariners paired Castillo with Bryce Miller, watched both pitchers bristle at the arrangement and then shifted to a six-man rotation that allowed everyone to remain a starter. It may have restored peace, but it hardly creates clarity. Seattle adjusted the plan around its pitchers’ preferred roles instead of asking those pitchers to fit the plan.

But the White Sox, a team that spent 2025 in the gutter, evaluated the pitcher standing in front of them, not the name, salary or résumé attached to him. When Castillo stopped giving them starter-quality innings, they stopped treating him like an unquestioned starter.

The Mariners Escaped the Most Dangerous Part of Castillo’s Contract

The Mariners received Seranthony Domínguez, outfielder Nolan Jones, catching prospect Boston Smith and cash considerations in the deal. Chicago also assumed approximately $30 million guaranteed to Castillo through 2027, with Seattle reportedly sending no money to cover the remaining obligation.

That financial escape grows more important after every Castillo appearance. Paying more than $24 million next season for a dependable mid-rotation starter would have been easier to explain. Paying it for a 34-year-old pitcher whose new team has already pushed him into the bullpen would spell doom in Seattle.

Instead, those innings will likely go to Kade Anderson and the rest of a younger rotation. Domínguez still has some improvements to make, but he gives the Mariners an experienced bullpen arm. Jones is a reclamation project and Smith is showing signs of being a future backup catcher. Most importantly, Seattle is no longer responsible for hoping Castillo reverses a decline that has followed him to Chicago.