Buster Posey's two-run shot in the first inning put the Giants ahead to stay and the San Francisco catcher later added an RBI single in the victory, which followed a 16-4 Giants rout in Friday's series opener.
Melky Cabrera added a solo homer -- finishing with a pair of RBI -- and drew four walks for the National League West-leading Giants, who stayed one-half game ahead of the second-place Los Angeles Dodgers with the win.
Madison Bumgarner (12-6) broke a personal three-game winless streak, striking out seven Rockies over six innings while allowing one run on five hits and a walk.
Jeff Francis (3-4) was rocked for six runs on nine hits over 3 2/3 frames for Colorado.
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