Just a year removed from pitching the 21st perfect game in major league history, Humber has had a terrible start to 2013. He is 0-7 with an 8.82 ERA.
Dallas Keuchel, who started in Triple-A this season before joining the Astros, will take start on Friday against Texas. Keuchel is 0-1 with a 4.96 ERA in six appearances.
Erik Bedard, who was moved into the bullpen after his last start on May 1, will return to the rotation to start on Saturday.
Houston manager Bo Porter wouldn't commit to keeping the current rotation and says competition among his pitchers makes it a "fluid situation."