Peters (elbow) will begin a rehab assignment at Double-A Altoona on Friday, Alex Stumpf of DKPittsburghSports.com reports.
Peters resumed throwing in late August and has been cleared to return to game action in the minors. The southpaw has been sidelined since Aug. 4 due to his elbow injury, so it's possible that he'll require more than one rehab appearance prior to rejoining the Pirates' bullpen.