Nick Hundley responded in the next half-inning by belting a lead-off triple off Edward Mujica (8-5) that just missed going out for a homer.
After the Marlins intentionally walked the bases full, Mike Dunn entered and surrendered a game-winning hit to Venable.
The San Diego right fielder also smacked a first-inning homer and Kevin Blanks followed with a two-run double as the Padres finished with 7-0 record against the Marlins this season.
Mike Stanton also homered for Florida.
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