Frazier knocked a three-run homer in the third inning and triggered a four-run outburst in the second with a run-scoring single as the Reds took the first of a four-game series.
Bronson Arroyo (7-6) yielded one run on just two hits over six frames, walked one and struck out three before rain halted the contest, posting his first victory in five starts.
Derrick Robinson added a pair of RBI in the victory.
Mike Kickham (0-3) was lit up for seven runs on nine hits over 2 2/3 innings for the Giants, who fell for the seventh time in eight games.
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