McCullers (shoulder) will throw a bullpen session Wednesday, Brian McTaggart of MLB.com reports.
The team has already confirmed that McCullers will begin the season on the DL due to the shoulder injury. He remains without a set timetable for a return to action, but a timetable should start to take shape as the right-hander ramps up toward a rehab assignment. Mike Fiers is expected to fill McCullers' rotation spot to open the season.