Votto knocked in runs in the first and fourth innings while Phillips contributed run-scoring at-bats in the fourth and sixth and Mesoraco drove home runs in the third and sixth as the Reds won for the fifth time in seven games since the All-Star break.
Mike Leake (10-4), who had three hits and scored a run as a batter, scattered 12 San Francisco hits and two walks over six innings but only allowed one run. That came on a Hunter Pence RBI single -- the second of Pence's five hits on the night -- in the third.
By then the Reds had reached Giants starter Chad Gaudin (4-2) for four runs. Gaudin ended up giving up six runs -- all earned -- on seven hits and five walks in 3 2/3 innings.
Shin-Soo Choo opened the game with a double and Votto got him home with a sacrifice fly. Cincinnati added three runs in the third with a two-out rally in which five consecutive batters reached base. Phillips, Jay Bruce and Mesoraco had hits that produced runs and a 4-0 lead.
Pence got one run back in the bottom of the inning but Votto and Phillips each knocked in runs the next inning in a rally that and chased Gaudin from the game. Phillips knocked in Votto and scored off a Mesoraco single in the sixth, making the score 8-1.
Pablo Sandoval had a two-run double in the eighth for San Francisco.
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