McCullers (shoulder) felt "great" after throwing a side session Wednesday, Brian McTaggart of MLB.com reports.
The 27-year-old resumed throwing over the weekend, and manager Dusty Baker is hopeful that the McCullers will be able to rejoin the Astros' rotation in mid-June. Baker said that the right-hander will throw in a simulated game during the team's upcoming road trip, and he could potentially progress to a rehab assignment afterward.