Luis Castillo didn’t invent a new pitch on Aug. 13. He found his old one. It’s almost been two weeks since the Mariners traded him to the White Sox. Suddenly, Castillo is looking like the pitcher who once anchored Seattle’s rotation. He overwhelmed another one of his former teams, the Reds, with seven scoreless innings, allowing one hit and two walks while collecting a season-high 10 strikeouts in a 5-0 White Sox victory.Sal Stewart singled in the first inning. It ended up being the only hit they could muster against Castillo. By the time the seventh inning rolled around, Castillo was still dealing, striking out the side to finish a 104-pitch performance.It’s not so much the performance, as it’s how he got it done. “La Piedra” leaned into his changeup, generating eight swings and misses with the pitch. The White Sox encouraged him to feature his “bugs bunny” pitch more prominently, reconnecting him with the weapon that helped establish him as one of baseball’s best starters during his years in Cincinnati.Luis Castillo tossed a 💎 with a season-high TEN PUNCHOUTS! pic.twitter.com/wpf8PfQDXA— Chicago White Sox (@whitesox) August 13, 2026Luis Castillo’s Changeup Faded From His Mariners Pitch MixThe Mariners never removed Castillo’s changeup entirely, but it played a support role instead of a defining one. In 2025, he used that pitch just 11.4 percent of the time. He leaned more on a four-seam fastball/sinker combo for almost 69 percent of his offerings.That was a major shift from the version of Castillo who built his reputation with a fastball-changeup combo. The velo is what grabbed the batter’s attention, but the changeup made the entire operation work.Seattle tilted Castillo toward the fastball. Part of it was because of his own command issues with it. Chicago has clearly worked with him on rediscovering it. On Wednesday, the old formula produced his best start of the season.The Mariners have earned their reputation as one of baseball’s better pitching organizations. But sometimes a successful development system can become too committed to its own preferences. Pitchers begin fitting the plan instead of the plan fitting the pitcher. Castillo’s declining changeup usage now deserves another look because the White Sox immediately identified the pitch as an important part of rebuilding him.Whatever combination of game planning, organizational philosophy and Castillo’s own confidence created his pitch mix when arriving in Seattle. The Mariners owned the final product. They watched his signature pitch drift into the background while his results deteriorated.One dominant outing doesn’t change the reality of Castillo’s difficult season, either. This could be chalked up with a vintage Castillo night. He allowed five earned runs in four innings during his White Sox debut and still owns a 4.96 ERA.The trade evaluation and Seattle’s handling of Castillo are separate conversations. The Mariners may have made a sensible deal after failing to maximize the version of the pitcher they traded. That may be worth looking at down the road. Regardless, the Mariners shouldn’t panic. They have plenty more to worry about. However, if Castillo’s resurgence continues, Seattle will have to confront the possibility that its pitching operation became too rigid with a veteran whose best path forward was getting back to basics.Add us as a preferred source on GoogleFollow