Luis Castillo turned back the clock Wednesday night, looking every bit like the three-time All-Star the Chicago White Sox traded for in his home debut at his new ballpark, and one pitch was at the center of his revival.
When the White Sox acquired Castillo, he was a long way from the pitcher who had spent years anchoring the front of the Cincinnati Reds and Seattle Mariners rotation. His 5.06 ERA was a career worst, his 19.4% strikeout rate a career low, and the Mariners had even begun experimenting with him as a piggyback reliever, a far cry from the role he had carved out as a three-time All-Star.
A change of scenery appears to be exactly what the doctor ordered. Castillo is once again viewed as one of the top dogs in a pitching staff, but perhaps more importantly, he has been given a fresh set of eyes to dissect his arsenal and identify what went wrong.
One of the most glaring issues in Castillo’s sudden decline has been his abandonment of the changeup, which was once one of the most devastating pitches in baseball. In 2019, the pitch carried a +28 run value, generated a 47% strikeout rate, and held hitters to a .133 expected batting average.
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But the changeup gradually faded from a weapon to a liability. Its run value fell to -5 in 2022, then -10 in 2023 and -8 in 2024. By 2025, Castillo had all but abandoned the pitch, throwing it just 11.4% of the time compared with 32% in 2019, while opponents posted a .329 expected batting average against it.
While the White Sox targeted Castillo primarily for his track record as a workhorse and postseason experience, rediscovering his changeup emerged as a potential key to helping the veteran right-hander return to form.
On Wednesday, the 33-year-old showed flashes of the pitcher who finished fifth in the 2023 Cy Young voting, tossing seven scoreless innings of one-hit ball against the Reds while racking up a season-high 10 strikeouts and generating 22 swings and misses, the most by a White Sox pitcher in a single game this season. While he did issue a pair of walks, Castillo was otherwise in complete control against his former club.
Of his 104 pitches, Castillo turned to his changeup 20 times (19.2%), a significant increase from his typical usage rate this season.
“It was about time for me to start having confidence in that pitch,” Castillo told reporters through an interpreter after the game. “I haven’t thrown it much but coming to this game that was the plan, to throw more changeups and it was effective today.”
As a result, five of Castillo’s 10 strikeouts came on the changeup, bookended by Elly De La Cruz chasing an 88 mph changeup to open the night and Michael Toglia swinging through one at the bottom of the strike zone to end Castillo’s outing in the seventh inning, sending the right-hander off the mound with a fist pump.
Castillo’s 22 whiffs were the most by a White Sox pitcher since Garrett Crochet recorded 24 against the Colorado Rockies on June 30, 2024, with eight of Castillo’s coming on the changeup. But the pitch’s effectiveness was amplified by his command of the four-seam fastball, which also generated eight whiffs and kept hitters from sitting on the changeup.
But it was Castillo’s battery mate who offered perhaps the simplest, and most fitting assessment of his performance.
“He’s a dog. I saw it firsthand, up close and personal,” catcher Drew Romo told reporters. “He’s a dog.”
The more confidence that Castillo can find in his changeup, the better this trade will age for the White Sox. Castillo is under contract through at least the 2027 season, with a $25 million vesting option for 2028 if he reaches 180 innings in 2027.
He has already proven he can anchor a starting rotation, leading the majors in games started in 2021 and 2023 while throwing 170-plus innings in six of his 10 seasons. Because of this, Castillo is likely going to be on the South Side for the next three seasons for better or worse.
If he can turn Wednesday’s performance into a trend rather than a one-night flash, the White Sox may have uncovered far more than a workhorse.
