The Padres scored a single run in each of the final three innings to overcome a 2-0 deficit.
Pinch-hitter Brad Hawpe drew a one-out walk in the ninth off Nick Masset (0-3). Hundley singled Hawpe to third and, after Will Venable was walked intentionally to load the bases, Hawpe was thrown out at home on a fielder's choice grounder from Jason Bartlett.
Hudson then hit the first pitch he saw from Masset into left for the game-winning single. Hudson also scored the game-tying run in the eighth on a ground out by Jorge Cantu. A sacrifice fly from Hundley in the seventh started the San Diego comeback.
The win went to Heath Bell (1-0), who worked a perfect top of the ninth. Cincinnati had won the first two games of the series.