The Astros announced the move Tuesday after a 3-1 loss to the Atlanta Braves.
Abad (1-4) took the loss in a 3-2 setback to the Braves on Monday. He has an 7.43 ERA in 22 games, allowing 18 hits and walking eight in 13 1-3 innings.
The 26-year-old Rodriguez is 2-3 with two saves and a 1.29 ERA in 13 games at Oklahoma City. The Astros are desperate for help in their bullpen, which has a 5.18 ERA and just five saves in 16 chances.