In five starts with the Pirates Nova has gone 4-0 with a 2.87 ERA and one complete game. He has struck out 22 and walked one.
Overall this season, the 29-year-old has gone 11-6 with a 4.41 ERA and three complete games, including one shutout.
Polo, 22, hit .289 with 16 homers in 109 games between Class-A Bradenton and West Virginia this season and was selected as a South Atlantic League Midseason All-Star.
Tarpley, 23, was 6-4 with a 4.32 ERA and 90 strikeouts in 100 innings in 20 starts with Class-A Bradenton.