The Astros have activated right-hander Wilton Lopez from the 15-day disabled list and optioned David Carpenter to Triple-A Oklahoma City.
Lopez hasn't pitched since June 10. The 28-year-old, who was on the DL with a right elbow sprain, is 3-0 with a 2.51 ERA in 32 appearances out of the bullpen. He has been a valuable cog in Houston's bullpen since 2010, when he burst onto the scene with a 2.96 ERA in 68 games.
Carpenter has surrendered 43 hits and 14 walks in 29 2/3 innings. He heads to Oklahoma City after posting a 6.07 ERA in 30 appearances with the Astros.
Houston is also expected to activate outfielder Justin Maxwell from the DL in time for Friday's game in San Francisco. Maxwell has been sidelined since June 26 with loose bodies in his left ankle.
Zack Meisel is a reporter for MLB.com. Follow him on Twitter @zackmeisel. This story was not subject to the approval of Major League Baseball or its clubs.