The Pirates have demoted Gregory Polanco to Indianapolis, Ken Rosenthal writes. There's no confirmation on what the corresponding move might be, although the Pirates could be promoting Jose Tabata. Polanco will, surely, return next week, when rosters expand.
If the Pirates are replacing Polanco with Tabata for the time being, it may simply be a matter of adding another right-handed bat. (The Bucs have a series coming up against the Cardinals, who have three lefties in their bullpen.) Also, Polanco probably isn't going to be a Super Two player now, but the threshold is uncertain, so getting him out of the majors for another week further reduces the likelihood that Super Two will be a problem.
In general, though, Polanco hasn't played much recently, with Clint Hurdle lately preferring Travis Snider. After a good first month in June, Polanco has struggled in July and August. Many fans expected him to be some sort of franchise savior right away, but that obviously hasn't proven to be the case. He's still an incredibly exciting talent, and I'd still bet heavily on him becoming a star, but adjusting to big league pitching isn't easy.