Reynolds led off the inning with a ground-rule double off Jeff Bennett (2-2) that bounced into the Atlanta bullpen down the right-field line. Reynolds moved to third on Miguel Montero's sacrifice bunt.
With the infield playing in, Byrnes hit a dribbler up the middle.
Tony Pena (5-2) pitched two perfect innings for the win.
Javier Vazquez blanked the Diamondbacks through six innings but didn't make it through the seventh.