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With the Chicago White Sox barely hanging onto a playoff spot, they’re making a significant change to the starting rotation.
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White Sox manager Will Venable announced on Thursday that starting pitcher Luis Castillo is moving to the bullpen.
Venable: Luis Castillo moved to bullpen.
Castillo with White Sox:
29 IP
7.76 ERA
1.79 WHIP pic.twitter.com/ESiGzL2hIX
— Underdog MLB (@UnderdogMLB) September 17, 2026
Chicago acquired Castillo from the Seattle Mariners during the MLB trade deadline, and he has struggled immensely. After allowing three runs on four hits and three walks in a bulk-relief outing on September 12 against the St. Louis Cardinals, Castillo has a dismal 7.76 ERA in seven appearances (six starts) and a 1.79 WHIP across just 29 innings.
In what is now his final start of the season, the 33-year-old allowed six earned runs on six hits, with two walks, a home run and just three strikeouts in four innings on September 3 against the Houston Astros. Castillo was set to start Friday against the Detroit Tigers, but David Sandlin will start instead.
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Castillo has had a disappointing season overall. In 27 games (23 starts), the righty-hurler is 4-11 with a career-worst 5.67 ERA, 111 strikeouts and a WHIP of 1.48 in 128.2 innings.
The White Sox shaking up their rotation in this way should come as no surprise. After losing two of three to the Cleveland Guardians this week, they have now lost seven of their last 10 and fallen to second place in the AL Central, but remain just a half-game behind Cleveland. The White Sox, though, hold a one-game lead over the Texas Rangers for the third and final Wild Card spot in the American League.
Chicago begins a crucial four-game series against the aforementioned Tigers on Thursday at Rate Field.
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More on the Chicago White Sox
- Detroit Tigers at Chicago White Sox MLB Prediction, Picks, Odds for Sept. 17, 2026
- Will Venable Comments on Munetaka Murakami’s Brutal Slump
- Chicago White Sox at Cleveland Guardians MLB Prediction, Picks, Odds for Sept. 16, 2026
- White Sox GM Comments on Troubling Luis Castillo Development
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This story was originally published September 17, 2026 at 3:43 PM.