Castillo had been sidelined since June 17 with a strained left oblique. He's hitting .196 with five homers and 15 RBIs in 34 games this season. He went 5-of-21 in a five-game rehab stint at Double-A and Triple-A recently.
In a corresponding move, the White Sox optioned catcher Zack Collins back to Triple-A Charlotte on Monday evening. Collins had struggled mightily, hitting .077 (2-of-26) in nine games since being called up in June.