Castillo (hamstring) was activated from the 10-day disabled list ahead of Saturday's tilt with Arizona, Jeff Sanders of The San Diego Union-Tribune reports.
Castillo will return to action after landing on the disabled list July 7 with a right hamstring strain. In 13 games out of the bullpen this season, he's posted a 2.84 ERA and 0.79 WHIP with 18 strikeouts over 12.2 innings.