Collmenter (4-2) struck out five without issuing a walk and joined Randy Johnson as the only Arizona pitchers to face the minimum over nine innings. Johnson accomplished the feat in his perfect game on May 18, 2004 against the Atlanta Braves.
The Arizona right-hander gave up leadoff hits in the third, fourth and sixth innings, but induced a double play directly after each hit to keep the Reds at bay.
Aaron Hill had three hits, including a solo homer, and drove in two runs, while Martin Prado went 2-for-4 with an RBI and a run scored for the Diamondbacks, who have won two straight and three of their last four games.
Tony Cingrani (2-5) allowed three runs -- two earned -- on seven hits over five-plus frames to absorb the loss. Brayan Pena registered two of the three hits for the Reds, who have lost five of their last six games.