Johnson (elbow) will begin a minor-league rehab assignment with Triple-A Pawtucket on Wednesday, Chris Cotillo of MassLive.com reports.
Johnson will pitch two innings for the PawSox on Wednesday, and if everything goes off without a hitch, the southpaw will throw three or four innings in his next rehab appearance, likely to come Monday. Seeing as Johnson has been sidelined since April 6, he'll likely need to make a handful of rehab starts before being cleared to rejoin the big club.