Zach Duke threw six innings of three-run ball and Pedro Alvarez hit a three-run homer to push the Pittsburgh Pirates to a 6-4 win over the Houston Astros on Saturday.

Houston got on the board early with an RBI single from Chris Johnson in the second inning before Alvarez answered with a three-run shot in the third inning, his 13th of the season.

Humberto Quintero evened it 3-3 with a two-run double in the fourth, while Jose Tabata and Ryan Doumit added RBI singles in the fifth inning for the Pirates.

Duke (8-14) allowed the three runs on seven hits while striking out three and walking one. Joel Hanrahan gave up a run in the ninth, but then shut the Astros down to earn his sixth save of the season.

Andrew McCutchen and Alvarez both finished with two hits for the Pirates, while Johnson and Quintero each had a pair of hits for Houston.

Houston starter Bud Norris (9-9) gave up five runs on seven hits over 4 2/3 innings, snapping a personal three-game winning streak.