The Astros placed left-hander Wandy Rodriguez on the 15-day disabled list Saturday and called up Jordan Lyles from Triple-A Oklahoma City.
Rodriguez was scratched from Saturday's start against Arizona after complaining of soreness in his left elbow. An MRI revealed fluid buildup in the joint.
Lyles will make his major league debut Tuesday against the Cubs in Chicago.
Rodriguez is 3-3 in 10 starts this season with a 3.41 ERA.