Abad opened the season with Houston and made 30 appearances out of the bullpen before he was optioned to Triple-A on July 28 to clear a roster spot for Armando Galarraga, who was designated for assignment on Wednesday.
In 30 appearances with Houston, Abad held a 3.86 ERA -- he surrendered 10 earned runs over 23 1/3 innings.
After he was optioned, Abad made three relief appearances with Oklahoma City before he was added to the team's starting rotation. In three starts, he allowed seven earned runs over 14 innings -- good for a 4.50 ERA. His most recent start was his most impressive -- Abad gave up two runs over 5 1/3 innings against Round Rock.
"I saw him two or three times down there -- looks like a different pitcher in the starting rotation," said DeFrancesco, who was the manager of Oklahoma City before taking over for the Astros on Sunday. "Good fastball, good breaking ball and an outstanding changeup. He's just another different look for us, we're excited about him and hopefully this role will be better for him."
Abad will square off against National League Cy Young Award candidate R.A. Dickey, who will attempt to notch his 16th win of the season. Dickey last pitched against the Astros on April 30, allowing three runs over six innings in a 4-3 Houston win.