The Pirates placed Valdez on the 10-day injured list Saturday with a strained left hamstring.
Valdez made an early exit from Friday's contest after injuring himself while running out of the batter's box, and he'll now officially remain out of action until at least Sept. 23. Jake Mangum is set to start in right field Saturday against the Cubs and could see regular playing time until Valdez returns. Meanwhile, Ronny Simon will come up from Triple-A to replenish Pittsburgh's outfield depth.