Polanco made his major league debut on June 10 but has slumped since the All-Star break. The 22-year-old had just one hit in his final 30 at-bats before heading back to Indianapolis.
Manager Clint Hurdle gave Polanco a handful of days off over the last two weeks hoping the rest would help. Polanco went hitless in a 4-3 loss to Milwaukee on Sunday.
Tabata is hitting .289 in 62 games with the Pirates this season but has spent most of the summer in Indianapolis following Polanco's promotion.