PITTSBURGH -- Pedro Alvarez is finishing his rookie season with a flourish.

Alvarez hit a three-run homer and Zach Duke pitched into the seventh inning for the second consecutive start, leading the Pittsburgh Pirates to a 6-4 victory over the Houston Astros on Saturday night.

The second overall pick in the 2008 amateur draft, Alvarez has reached base safely in 13 straight games and 23 of his last 24. He is hitting .237 with 13 home runs and 54 RBIs in 88 games.

"Pedro has been working really hard all year and now he is starting to see results," Pirates manager John Russell said. "He's really swinging the bat well."

Alvarez was 1 for 7 with five strikeouts against Houston starter Bud Norris before his home run into the right-field stands in the third inning tied the score at 3.

"The biggest thing about playing in the major leagues is the adjustments you have to make," Alvarez said. "You're constantly adjusting every single day. I hadn't had much success [against Norris] but I wasn't thinking about that when I was at the plate. Now that I've seen him a few times, I know better what to expect."

Alvarez helped the Pirates win for the sixth time in eight games and bounce back with a victory one night after losing their 100th game of the season.

"We really hadn't done anything until that point and then Pedro really gave us a big lift with the home run," Russell said. "It seemed to get everyone going."

Pittsburgh took the lead for good in the fifth against Norris (9-9) when Jose Tabata and Ryan Doumit hit RBI singles to break a 3-all tie. The Pirates added a run in the eighth when Alvarez scored on a wild pitch by Matt Lindstrom.

Duke (8-14) was pulled after giving up Humberto Quintero's leadoff single in the seventh. The left-hander allowed three runs and seven hits while walking one and striking out three.

"Zach didn't have his best stuff, but he really kept battling all night long and gave us a quality start," Duke said.

Duke tossed 7 1/3 innings in a no-decision against Arizona last Sunday. He had not made it into the seventh in back-to-back starts since pitching seven innings against Atlanta on April 10 and Cincinnati on April 16.

"The season obviously hasn't gone the way I'd like, but it would be nice to finish up on a good note and have something to feel good about going into the winter," said Duke, whose last start of the year will be Thursday night at Florida.

Joel Hanrahan gave up an RBI double to pinch-hitter Brian Bogusevic with two outs in the ninth, then retired Geoff Blum on a grounder for his sixth save.

Alvarez and Andrew McCutchen each had two hits. McCutchen also scored twice as Pittsburgh rallied from a 3-0 deficit.

Norris had his three-start winning streak snapped -- he was tagged for five runs and seven hits in 4 2/3 innings. Houston had won his previous six starts.

"It wasn't like it was missing by a lot, but they were enough to get him in the hole a little bit," Houston manager Brad Mills said. "Four of the five runs he gave up were with two outs, and that was big. We've talked about not letting innings build and being able to close out innings, and those things are big. Tonight it was them coming through with two-out hits that hurt us."

Quintero had two hits, including a two-run double in the fourth that gave the Astros a 3-0 lead. Houston opened the scoring in the second when Jason Michaels led off with a double and came home on a single by Chris Johnson, who had two hits.

The loss was Houston's fourth in five games.

Game notes
Pittsburgh RF John Bowker left the game after the fourth inning with a sore left knee. ... RHP Jeff Karstens, who has not pitched since a start on Aug. 31, hopes to work in relief during the Pirates' season-ending road trip that begins Monday. ... At 74-81, Houston must win its last seven games to avoid having back-to-back losing seasons for the first time since 1990-91. ... Astros coaches Brad Arnsberg, Dave Clark, Bobby Meacham, Al Pedrique and Jamie Quirk all signed two-year contract extensions. Hitting coach Jeff Bagwell wants to mull over his decision about coming back next season.