With the game knotted 4-4 in the eighth, the Giants loaded the bases with two outs and Belt responded in the clutch, grounding a 3-1 pitch from Brad Ziegler (1-1) up the middle for two runs.
Belt also socked a solo homer while Marco Scutaro went 3-for-4 with two runs scored as San Francisco ended its losing streak with a victory in the first of a three-game road set.
Jean Machi (1-0) earned the decision with a scoreless seventh inning and Sergio Romo tossed a 1-2-3 ninth for his ninth save.
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