With the scored tied 1-1, Gregor Blanco led off the eighth with a single off Rex Brothers (1-2).
Matt Belisle relieved and Blanco went to second when Joaquin Arias laid down a bunt single that Rockies catcher Wilin Rosario managed to field. But he threw wildly to first, allowing Blanco to advance to third on the play.
One out later, Posey smoked a grounder up the middle, breaking the deadlock, and Pill later made it 3-1 on another run-scoring single through the hole.
Colorado starter Christian Friedrich yielded only one run on six hits in a seven-inning effort.
Rosario belted a solo homer for the Rockies.
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