Troy Tulowitzki's three-run homer keyed a seven-run outburst in the eighth inning - all with two outs - as the Colorado Rockies surged past the visiting Arizona Diamondbacks 8-3 on Tuesday.

The loss was only the second in the last 14 games for the Diamondbacks, whose lead in the National League West fell to six games over the San Francisco Giants.

The Rockies cut Arizona's lead to 3-2 on an RBI single by Carlos Gonzalez before Tulowitzki's blast against reliever David Hernandez (3-3) - his 30th home run of the year - made it 5-3. Seth Smith tripled home a run and scored on a base hit by Jordan Pacheco before Dexter Fowler capped the blitz with a bases-loaded walk.

Matt Belisle (10-4) retired the lone batter he faced in the eighth. Colorado starter Jason Hammel gave up two runs (one earned), six hits and struck out six in seven innings.

Gerardo Parra gave the Diamondbacks a 2-1 lead in the seventh with an RBI single, and Arizona doubled its lead in the eighth when Pacheco committed a throwing error on an infield hit by Miguel Montero.

Josh Collmenter allowed one run on five hits in 6 1/3 innings and struck out four.