Saunders (1-0) yielded six hits, walking two and striking out five as the Diamondbacks won the opener of a three-game series.
Young went 3-for-4 while Gerardo Parra and Aaron Hill each added a solo homer for Arizona.
Pirates starter Erik Bedard (0-3) was saddled with the loss despite yielding only a pair of runs on three hits. He walked four batters and fanned three.
Neil Walker notched the lone RBI for Pittsburgh, which lost its sixth game in seven outings.