Valdez will make his first start of the season Saturday against the Orioles, Chandler Rome of the Houston Chronicle reports.
The Astros made a few roster moves Tuesday, including sending starter Corbin Martin back to Triple-A Round Rock. Valdez, a minor-league starter who pitched four scoreless innings in relief of Martin on Monday, becomes Houston's No. 5 starter for the moment. The left-hander gets a soft entry against a Baltimore team that ranks 25th in MLB with a .708 OPS.