McCullers (neck) was activated from the 10-day injured list to start Wednesday's game against the Rangers, Brian McTaggart of MLB.com reports.
The 26-year-old underwent a procedure Sept. 8 which alleviated most of his neck pain, and he'll rejoin the rotation after spending the 10-day minimum on the shelf. McCullers has a 5.79 ERA, 1.42 WHIP and 32:16 K:BB across 37.1 innings this season.