Lopez on DL with elbow injury
Lopez is 0-1 with a 7.71 ERA in six appearances this season. He was 5-2 with a 2.96 ERA in 68 appearances last season.
His time on the disabled list is backdated to Thursday.
Houston also purchased the contract of 28-year-old Jose Valdez from Triple-A Oklahoma City on Friday. Valdez is 1-0 with a 2.45 ERA and two saves in three appearances for the RedHawks this season. This is the first time Valdez has been in the majors.