Luis Castillo allowed three earned runs on four hits and three walks with two strikeouts in 2.2 innings on Saturday night in the Chicago White Sox's 6-5 win over the St. Louis Cardinals. Castillo also allowed a runner to score that he inherited from Sean Newcombe, who pitched 1.1 innings as the opener.

Castillo should only appear in games with decisive margins for the rest of the regular season. If the White Sox hold on to their playoff spot, Castillo should not be on the postseason roster. The White Sox acquired Castillo from the Seattle Mariners in August.   

Castillo has a 7.76 earned run average in 29 innings, allowing 41 hits, 11 walks, 26 runs, 25 earned runs and 25 strikeouts in seven games with six starts for the White Sox. Other than shutting out Cincinnati in seven innings on Aug. 12, Castillo has allowed at least three runs in every White Sox appearance.

The White Sox acquired Castillo for reliever Seranthony Dominquez and minor leaguers Nolan Jones and Brandon Smith at the trade deadline. Trading Dominguez rid the White Sox of a two-year, $20 million contract he signed in January. Castillo was acquired as a veteran pitcher with postseason experience. 

Luis Castillo struggled with Seattle

Castillo had three wins and nine losses with a 5.06 ERA in 99.2 innings, 32 walks, 86 strikeouts and a 1.395 WHIP with Seattle. With the White Sox, Castillo has a 1.709 WHIP. Entering 2026, Castillo had seven consecutive seasons with an ERA below 4.00. 

The White Sox bailed out Castillo after rallying from a 4-1 deficit. After tying the game at four, the White Sox trailed St. Louis 5-4 entering the ninth inning. Randall Grichuk hit a two-out, two-strike, two-run home run to put the White Sox ahead 6-5 and eventually earn the critical win. 

The White Sox's win over the Cardinals reduced their magic number to clinch a playoff spot to 13. The magic number to clinch the American League Central is 14. Cleveland hosts the White Sox in a three-game series from Monday through Wednesday that could decide who wins the AL Central.