The second came from reliever Sean Burnett's left hand in the sixth inning. Lance Berkman launched it over the fence for a two-out, three-run homer, giving the Astros the lead for good.

"I got two quick outs, then kind of let it slip away and gave the game away," Burnett said. "You've got to finish the inning, and that's what I didn't do."

With the game tied, 3-3, Burnett (0-1) was unable to close out the sixth against either Michael Bourn, who doubled to center, or Miguel Tejada, who walked.

Burnett got ahead in the count, 1-2, when Berkman swung over a low slider. Mindful that righties have hit at a .306 clip against him, Burnett rode his confidence in his slider and opted to come back with another.

"I was looking to bury it in the dirt, just like the one before," Burnett said. "I left it up to a good hitter, and he made me pay."

It was Berkman's second home run of the season -- and his first hit in six career plate appearances against Burnett. It enabled the Astros to take two out of three games in the series and notch back-to-back wins for the first time this year.

With the Pirates clinging to a 3-2 lead in the fourth inning, Karstens got two quick outs. Jeff Keppinger tripled to center field.

That brought up Ortiz, who had flied out with two runners on in the second inning. Karstens fired a first-pitch slider, and Ortiz lined an RBI single.

Before Karstens went back onto the mound, shortstop Jack Wilson walked over.

"Didn't they tell you (Ortiz) is a good hitter?" Wilson asked.

That was news to Karstens, who later second-guessed the pitch selection.

"Maybe if I throw a fastball there ..." Karstens said. "In his first at-bat, we started him off with a breaking ball with runners on. It's just something I've got to look at."

In his season debut, Karstens labored to get through four innings with 87 pitches. He allowed three runs on four hits, walked five and struck out one.

"Good and bad," manager John Russell said. "He got his pitch count up quick. When he was on, he kept the ball down. He looked rusty."

Karstens was supposed to pitch last Friday in Cincinnati. But the game was rained out, and his turn in the rotation was skipped.

"It felt like it'd been forever since I was out there," Karstens said. "But I felt good. The ball felt good coming out of my hand.

"It doesn't come down to being rusty. The bullpen session I had two days ago went really well. I just didn't throw the ball over the plate today."

The Pirates had a chance to tie the game in the seventh.

With two runners on base, Freddy Sanchez had a 17-pitch duel against reliever Chris Sampson. Sanchez fouled off 13 pitches, staying alive and hoping to coax a mistake out of Sampson.

With the crowd chanting his name, Sanchez blasted the 17th pitch to deep center field ... where Bourn tracked it down for an out.

"You see that (kind of at-bat) every once in a while," Russell said. "It would've been better if he'd have gotten a hit. He battled, and that's all you can ask."

How they scored

> Pirates first inning (Russ Ortiz pitching)

Nyjer Morgan doubled to right field. Jack Wilson bunted out to first base, sacrifice; Morgan to third. Wild pitch, Morgan scored. With two outs, Nate McLouth singled to right. Adam LaRoche doubled to center, McLouth scored.

Pirates 2, Astros 0

Astros second (Jeff Karstens pitching)

With one out, Hunter Pence hit a solo home run (No. 3) to left on a 1-1 pitch.

Pirates 2, Astros 1

Pirates second

With two outs, Karstens walked. Morgan tripled to center, Karstens scored.

Pirates 3, Astros 1

Astros third

Michael Bourn walked. Bourn stole second. Miguel Tejada grounded out to third, Bourn to third. Lance Berkman walked. Carlos Lee grounded to shortstop, fielder's choice; Berkman out at second; Bourn scored.

Pirates 3, Astros 2

Astros fourth

With two outs, Jeff Keppinger tripled to center. Ortiz singled to left, Keppinger scored.

Pirates 3, Astros 3

Astros sixth (Sean Burnett pitching)

With two outs, Bourn doubled to center. Tejada walked. Berkman hit a three-run homer (No. 2) to left on a 1-2 pitch.

Astros 6, Pirates 3