Peters elected free agency Oct. 6.
Peters cleared waivers Saturday and was outrighted to Triple-A Indianapolis, Alex Stumpf of DKPittsburghSports.com reports.
Peters was designated for assignment by the Pirates on Thursday.
Peters (elbow) will begin a rehab assignment at Double-A Altoona on Friday, Alex Stumpf of DKPittsburghSports.com reports.
Peters (elbow) threw in Philadelphia on Friday, Justice delos Santos of MLB.com reports.
Pirates director of sports medicine Todd Tomczyk said Wednesday that Peters (back) should be ready to start a throwing program soon, Alex Stumpf of DKPittsburghSports.com reports.
The Pirates placed Peters on the 15-day injured list Thursday due to left elbow inflammation, Alex Stumpf of DKPittsburghSports.com reports.