McCullers (back) threw another bullpen session Thursday, Brian McTaggart of MLB.com reports.
McCullers continues to trend in the right direction, as he's now completed his second bullpen session since landing on the disabled list at the end of July. He should progress to facing live hitters soon, and if all goes well, he'll likely head out on a minor-league rehab assignment shortly thereafter. Barring any setbacks, it's looking like he could rejoin the big-league rotation near the beginning of September, though a clearer timetable should become available once his rehab assignment is set.