Johnson, who left his start Wednesday with shoulder discomfort, is headed back to Boston on Thursday for evaluation, Jen McCaffrey of MassLive.com reports.
Johnson said he felt some discomfort while warming up prior to the game, and when pitching coach Carl Willis visited the mound during the third inning, the left-hander admitted to the discomfort. The hope is that Johnson didn't pitch too long with the injury which could set him back. If Johnson is forced to miss his next scheduled start Monday, the Red Sox could use Hector Velazquez, who has started one game for Boston this season and picked up the win Wednesday after replacing Johnson in the third inning.