McCullers (forearm) completed a 15-pitch bullpen session Tuesday, Danielle Lerner of the Houston Chronicle reports.
McCullers threw changeups and two-seam fastballs, which averaged about 86 mph. The 28-year-old's velocity sat in the low 80s during his previous bullpen session, and he continues to ramp up his throwing program. McCullers is scheduled to take the mound for another bullpen session Friday.