Miguel Montero had a two-run homer among three hits as the Arizona Diamondbacks reduced their magic number to two with an 8-5 triumph over the visiting Pittsburgh Pirates on Wednesday afternoon.

Ryan Roberts and Aaron Hill also had two RBIs apiece for Arizona, which increased its lead over San Francisco in the National League West to six games with six remaining. The Giants play at Los Angeles on Wednesday night.

The Diamondbacks, who registered a season-high five stolen bases, also pulled within one game of NL Central-leading Milwaukee for home-field advantage in the division series.

Montero capped a three-run first with his 18th blast of the season off Ross Ohlendorf (1-3), who yielded seven runs in two-plus innings. Roberts delivered a two-run double in the third and Hill plated two with a single later in the frame for an 8-1 lead.

Rookie Wade Miley (4-2) allowed two runs over five innings en route to his fourth win in five decisions. The 24-year old has surrendered two runs or less in five of his seven major-league starts.

J.J. Putz struck out the side in the ninth for his franchise record-tying 22nd consecutive save and 43rd in 47 chances this season. Putz tied the club mark set by Gregg Olson from June 13-Sept. 22, 1998.

Derrek Lee went 3-for-4 with a homer and two RBIs for Pittsburgh, which has lost 10 of 13. Lee has recorded seven home runs and 18 RBIs in 22 games since being acquired from Baltimore on July 30.