McCullers (forearm) threw long toss Sunday and could begin throwing off a mound before the end of April, Brian McTaggart of MLB.com reports.
The right-hander has been throwing mostly fastballs but is also close to integrating his offspeed pitches. McCullers doesn't have a clear timetable to be activated from the injured list, but his return to mound work will be a significant step in his rehab progress.