Duffy (hamstring) will begin a rehab assignment Thursday, Marc Topkin of the Tampa Bay Times reports.
Duffy hasn't played at the big-league level all season as he's dealt with multiple setbacks while recovering from a hamstring strain. He spent some time on a rehab assignment in May before being shut down late in the month. He's nearly ready to get back to some game action, but he still isn't particularly close to suiting up in a big-league contest.