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HOUSTON (AP) -- Once Tim Lincecum left with a knee injury, the Houston Astros had their way with San Francisco's pitchers.

Lance Berkman hit a grand slam in an eight-run seventh, two innings after Lincecum left the game with a bruised right knee, and the Astros beat the Giants 12-4 on Tuesday night for their sixth straight victory.

Lincecum allowed one hit and struck out seven before he was hit in the knee by Brad Ausmus' line drive in the fifth. The Giants' ace limped off the field and was taken for X-rays which Giants manager Bruce Bochy said were negative. He said Lincecum would be re-evaluated Wednesday.

"It caught him in a good spot," Bochy said. "It paralyzed him for a little bit. But he's walking around pretty good now. That's good news. That's the only good news we got tonight."

Lincecum did not speak to reporters after the game.

"The concern was there and you're hoping for the best," Bochy said. "It hit him good and there's not a lot of meat on those bones."

The Astros hammered four San Francisco relievers to blow open what had been a tight pitching duel between Lincecum and Astros ace Roy Oswalt (10-8).

"I hope he's all right," said Oswalt, who allowed 10 hits and struck out four in seven innings. "He's a great competitor, and I like the way he goes about his business."

The Giants led 3-2 with one out in the seventh when Alex Hinshaw walked Ausmus to spark the rally. Bochy brought in Tyler Walker (4-7) to relieve, but pinch-hitter Hunter Pence singled and Mark Loretta walked to load the bases.

Left-hander Jack Taschner replaced Walker and Darin Erstad blooped a two-run single to left and Pence scored right on Ausmus' heels. It was a less violent version of the end of the Astros' 5-4 win over the New York Mets on Aug. 2, when Pence followed Loretta across the plate in a three-way collision with Mets catcher Ramon Castro.

Miguel Tejada singled to load the bases again for Berkman, whom Lincecum had struck out twice.

This time, Berkman drove a 3-1 pitch off the brick facade in left field, his 24th homer this season and his fourth career regular-season grand slam. Berkman has homered in two of his last three games after going 33 games without one.

"The guy's a .300-plus hitter every year for a reason," Taschner said. "I put him in a hitter's count and he's not going to make a mistake."

Geoff Blum doubled, Geno Espineli relieved Taschner and Ty Wigginton added a two-run homer to right. Wigginton had three RBIs in Monday's 3-1 win, including a solo homer.

Pence added a solo homer and Tejada had an RBI double off Espineli in the eighth.

Randy Winn drove in two runs and Aaron Rowand hit a solo homer in the ninth for the Giants.

Erstad had an RBI double in the third and scored on an error by second baseman Emmanuel Burriss to give Houston a 2-1 lead.

Lincecum, a .163 hitter, singled up the middle in the fourth and scored on Winn's double to right center. Lincecum struck out the side in the fourth and had all the Astros baffled.

Berkman said Lincecum resembles a young Oswalt.

"If he's not the best young pitcher in the league, then I don't know who is," Berkman said. "He's very difficult, several different pitches. Explosive fastball, tough curveball that keeps you off-balance.

"He's a lot like Roy when Roy first came up," Berkman said. "If he learns to pitch like Roy has, he's going to be tougher all the time."

Fred Lewis and Molina started the fifth with singles. One out later, Oswalt walked John Bowker to load the bases and Lewis scored on Rich Aurilia's fly to right to put the Giants up 3-2.

Ausmus led off the Houston fifth and drove a 3-1 pitch back to the mound. Lincecum tried to dodge it, but the ball nailed him on the side of his knee. Ausmus was out on the play, but Lincecum hit the ground and later limped to the dugout. He was replaced by Keiichi Yabu, who got the last two outs.

Yabu and Hinshaw held Houston scoreless in the sixth, but the Astros put together their highest-scoring inning of the season in the seventh.

The Astros have won 10 of their last 12 games and have their first six-game winning streak since April 20-25. They improved to 60-59, their first time over .500 since June 10.

Game notes

Astros 2B Kazuo Matsui left after two innings with a sore back and was replaced by Loretta. ... The Giants have committed 30 errors in their last 36 games. ... Ausmus became the 25th catcher to score 700 runs.