The move is retroactive to Monday for Polanco, who is nursing a left hamstring strain.
Polanco is batting .252 with one homer and nine RBIs in 34 games this season. The 25-year-old Dominican is hitting .253 with 39 homers and 180 RBIs in 420 career contests — all with Pittsburgh.
Ortiz, who will be joining the Pirates for his second stint this season, is batting .253 with three RBIs in 27 games with Indianapolis.