Cahill made 19 appearances in a previous Arizona stint, going 1-6 with a 5.66 ERA. He was 0-4 with a 9.17 ERA as a starter.
Cahill was designated for assignment then optioned to Reno on June 12. He went 2-2 with a 3.49 ERA in six starts with the Aces.
Bolsinger was 1-6 with a 5.50 ERA in 10 games during two stints with the D-backs.