Pedro Alvarez and Derrek Lee homered while Charlie Morton pitched six scoreless innings as the Pittsburgh Pirates erupted for a 5-3 victory over the host Arizona Diamondbacks on Tuesday.

Arizona failed to take advantage of San Francisco's 2-1 loss to Los Angeles, and remained 5 1/2 games ahead of the Giants in the National League West with seven games remaining. The Diamondbacks' magic number for clinching their fifth division title is three.

The Diamondbacks also fell two games behind the Milwaukee Brewers for the second-best record in the NL.

Five different players - including Morton - had two hits for the Pirates, who scored five runs over their previous four games.

Alvarez gave Pittsburgh a 2-0 lead with a solo homer off Daniel Hudson (16-11) in the second inning and Lee belted a two-run shot in the eighth. Lee has recorded six home runs and 16 RBIs in 21 games for the Pirates since being acquired from Baltimore on July 30.

Morton (10-10) limited Arizona to three hits and three walks in halting a four-game losing streak and posting only his second win in 11 starts. Joel Hanrahan struck out two a perfect ninth for his 39th save in 42 opportunities.