McCullers (back) is scheduled to make a rehab start with Double-A Corpus Christi on Wednesday, Julia Morales of AT&T SportsNet Southwest reports.
McCullers is set to make his second rehab start as he continues to work his way back from a back ailment that has sidelined him for all of August. The 23-year-old walked five batters in three innings during his first rehab start, and he issued nine free passes over 14.1 innings before landing on the disabled list, so he'll need to show better control before the Astros consider bringing him back. If he's able to show improvement in his second start, he shouldn't be too far from activation.