Valdez (elbow) threw a 30-pitch bullpen session Saturday, Matt Kawahara of the Houston Chronicle reports.
Saturday's session marks the first time Valdez has thrown off a mound since elbow inflammation sent him to the injured list April 9. The Astros will wait to see how he recovers before determining his next steps, though manager Joe Espada said it's still possible the 30-year-old southpaw is able to return without embarking on a rehab assignment.