The Reds opened up a six-game lead over Arizona in the race for the National League's second wild-card spot.
Cincinnati remained third in the NL Central, but moved to 2½ games behind first-place Pittsburgh, which lost at San Diego.
Mike Leake allowed four runs in the fifth inning, but was dominant in his other five innings for first win in his past five starts.
Leake (11-5) allowed six hits and four runs with no walks and three strikeouts while the Reds were building an 8-0 lead.
Aroldis Chapman pitched the final two innings for his 32nd save -- his first career two-inning save.
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