Giles, who tied a major league record Sunday by hitting doubles in his first four at-bats, had Atlanta's fifth slam this season, a drive off Javier Vazquez (8-7) that capped a five-run sixth.
Vladimir Guerrero homered twice off Mike Hampton (7-5), including a 151-meter (502-foot) drive off the base of Olympic Stadium's middle deck. Hampton won his fourth straight start, allowing five runs -- four earned -- and eight hits before he was ejected in the sixth inning for arguing.
John Smoltz gave up a two-run single to Orlando Cabrera and an RBI single to Guerrero, then got his major league-high 38th save when Wil Cordero hit into a game-ending double play.
Marlins 3, Diamondbacks 2
In Miami, Miguel Cabrera drove in three runs and Mark Redman (9-4) gave up one run and six hits in 7 1-3 innings as Florida edged Arizona.
Florida has won seven of its past eight games, closing within one game of Philadelphia, the NL wild-card leader.
Miguel Batista (7-6) struck out a career-high 11 in seven innings for Arizona, which lost for the eighth time in 10 games and dropped 11 games behind first-place San Francisco in the NL West.
Florida first baseman Derrek Lee left in the eighth inning after partially dislocating a joint in his right shoulder.
Brewers 4, Mets 2
In New York, Scott Podsednik hit a tiebreaking two-run single in the ninth inning off John Franco as Milwaukee defeated New York.
The tiebreaker came Eddie Perez drew a one-out walk from David Weathers (1-5) and Royce Clayton bunted.
Reliever Leo Estrella (3-2) pitched 1 2-3 perfect innings for the win, while Dan Kolb pitched the ninth for his third save.
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