The Giants rallied from 4-2 deficit over the final two innings to pull out their fourth straight victory in the opener of a three-game series.
Then in the ninth, Torres led off with a single against Tony Sipp (1-1), went to second on Brandon Crawford's sacrifice and came home with the winning run when Belt lined a 1-1 pitch into left-center field.
Sergio Romo (1-1) was credited with the decision after recording the final out in the top of the ninth.
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