Mulvey, recalled from Triple-A on Wednesday, gave up two runs in three innings over two relief appearances for the D-backs. In four starts for the Reno Aces, the 24-year-old was 0-1 with a 4.05 ERA.
Valdez, called up from Reno, will be making his Major League debut when he starts against the Astros at Minute Maid Park. In four Triple-A starts this season, the 25-year-old Dominican right-hander is 1-1 with a 3.80 ERA. In parts of six seasons in Arizona's farm system, Valdez is 38-34 with a 3.49 ERA.
Alden Gonzalez is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.