Latos (4-3) held the Mariners to one run over six innings, allowing four hits, walking two and striking out five, to lift San Diego to a win in the rubber match of a three-game inter-league series.
Venable's RBI single in the seventh inning gave the Padres some breathing room with a 3-1 lead, and then San Diego broke the game open with five runs in the eighth. Venable capped the outburst with a sacrifice fly.
Nick Hundley socked a two-run double in the big inning, finishing 2-for-4 with two runs scored, and Chris Denorfia added a pinch-hit, two-run double for the Padres.
Felix Hernandez (2-4) took the loss despite surrendering just two earned runs on seven hits over seven innings.