SAN FRANCISCO -- The enigmatic Felipe Paulino continues to walk the line between dominance and disaster. He can stray to either side in the course of a pair of starts or even in the course of a few innings, like he did Friday night against the Giants.

Unfortunately for the Astros, Paulino spent more time flirting with disaster and had trouble locating his electric stuff.

Paulino was rocked for eight hits and seven earned runs in 4 2/3 innings and issued four walks and two wild pitches, allowing the Giants to snap a three-game losing streak with an easy 8-2 win over the Astros in the series opener at AT&T Park.

"It's a bad day," said Paulino, who's the first Astros pitcher to begin a season 0-6 since Chris Holt in 1999. "Nothing was working well today. It was a really bad day. I tried to do the best I could do."

Coming off a three-game sweep at the division-leading St. Louis Cardinals, the Astros failed to sustain the momentum in advance of Saturday's showdown between aces Roy Oswalt and Tim Lincecum. Houston managed only a solo homer by Hunter Pence (3-for-4) in the fourth and an RBI single by Lance Berkman in the eighth.

"You always kind of want to get that first game and not really pay attention to the others," shortstop Tommy Manzella said. "The first game of the series is the most important to try to get a little leverage, a little momentum and especially to keep the momentum we had from the Cardinals series. It didn't work out tonight. Seemed like everything they touched found its hole and sometimes it goes like that, and the score represented that."

The Astros have lost in 14 of Paulino's last 15 starts since July 3, 2009. Paulino, who had received the lowest run support in the National League, is 5-18 since joining the Majors in 2007.

"The thing was he was getting ahead of guys," Astros manager Brad Mills said. "I don't know how many times he got ahead of guys 1-2 and he wasn't able to put them away. That was the big issue, more than anything else."

Paulino was terrific in his previous start five days earlier against San Diego, striking out 11 batters and giving up five hits and one earned run while not walking anyone. He displayed some dominance Friday when he retired eight in a row at one point, including five by strikeout.

"He was mixing up his pitches," Giants outfielder Nate Schierholtz said. "He throws firm. He has a couple of offspeed pitches, too. We just got hits at the right time to put pressure on early."

Paulino was done in when the Giants scored three runs in the second and fifth innings to build a 7-1 lead. San Francisco left fielder Andres Torres proved to be a difficult out, going 3-for-4 with two doubles and a triple.

"He just never found a consistent rhythm," Astros catcher Kevin Cash said. "He came out and wasn't quite as sharp with his offspeed pitches and got behind in some counts, and then he had two innings or maybe three that he rolled right through. Then he fell back into that slot.

"We missed some 0-2 pitches, 1-2 pitches when we had some guys and maybe caught too much plate with them to good hitters. Sometimes you get away with them and sometimes you don't, and we definitely didn't get away with them tonight. Seems like every mistake or missed spot or bad selection on my part, it hurt us."

Paulino walked Torres with one out in the first, and he scored on an Aubrey Huff single. The Giants scored three times in the second to take a 4-0 lead on RBIs by Matt Downs, Torres and Pablo Sandoval. Paulino sent down eight in a row before giving up three runs in the fifth.

"There were a couple of base on balls in there, but there were one or two of them that were 1-2 and then he lost them," Mills said. "He's getting ahead of hitters like you'd like to, but he couldn't put them away."

The Astros were stymied by Giants starter Todd Wellemeyer, who gave up five hits and two runs in 7 1/3 innings. Pence hit his team-leading sixth homer of the season in the fourth inning, and Lance Berkman had an RBI single in the eighth off Guillermo Mota. Pence (.253) and Berkman (.256) continue to see their batting averages soar after slow starts.

"They're continuing to have good at-bats besides just getting hits," Mills said. "I think Lance had a couple of really good at-bats today."

Cash, who caught Paulino's previous start against San Diego, thinks the pitcher is close to putting it all together. For the Astros, that can't come soon enough.

"He's right on the brink of just taking off, I think," Cash said. "He's pumping 96, 97 [mph], and with the offspeed pitches that he has, he's real close. You just hate to see that one big inning -- three runs the first time and then mows them down for a couple of innings and gives up three runs again. Finding that rhythm is the biggest key for him."