The Phillies, who lead the NL in home runs and grand slams, broke the game open in the fourth inning when rookie right-hander Wilton Lopez came undone in his first Major League start. Lopez, a 26-year-old Nicaraguan, allowed six hits and five runs in 3 2/3 innings.
"I thought he did a great job up until then," Clark said. "He just got himself in a little jam there, and he left a bad pitch up to a pretty good hitter."
Philadelphia starter J.A. Happ (12-4) held the Astros to four runs (three earned) and nine hits in 5 2/3 innings to become the first Phillies rookie to win 12 games in a season since Jim Owens in 1959. The Astros had the tying run at the plate in the ninth inning against Ryan Madson, but he struck out Carlos Lee and Hunter Pence to end the game.
Unless the Astros win the final two games of the series against the Phillies and the Atlanta Braves win two in a row, Houston will have a front-row seat for Philadelphia's division-clinching celebration.
"You would like to be in the same situation, definitely," said Astros center fielder Jason Michaels, who played with the Phillies from 2001-05. "We came in here and tried to play good ball. I thought all in all we had good at-bats tonight. We were making these guys throw a lot of pitches."
Lance Berkman gave the Astros a 1-0 lead in the third with his 25th homer of the season, and the Phillies tied the score in the bottom of the inning on Jimmy Rollins' RBI double. Lopez allowed two singles and a walk to start the fourth to load the bases and prompt a visit from pitching coach Dewey Robinson.
"He said to try to throw strikes ad use the slider," Lopez said.
But Feliz crushed the next pitch -- a slider -- and sent it 396 feet and over the left-field wall for a grand slam to give Philadelphia a 5-1 lead. Werth hit a two-run homer to right field in the fifth off reliever Wesley Wright to stretch the lead to 7-2.
"The big grand slam from Feliz really, really put a damper on things for us," Clark said. "It's a pitch that Lopey left up. It looks like it was a hanging slider and he got the big part of the bat on it and we all know if you hit the ball good here it's a good chance to get out of the ballpark."
All three batters walked by Astros pitchers came around to score.
"Walks will definitely come back to haunt you, and they did for us tonight as well," Clark said.
Kazuo Matsui hit a two-run homer for the Astros in the sixth to extend his career high to nine homers. That was the last hit for the Astros until the ninth, when Matsui led off the inning with a single against Madson, who mowed the Astros down in the eighth. Berkman rolled a single to left one out later to put runners at first and second.
But Madson struck out Lee swinging on a 96-mph fastball and caught Pence looking to end the game on a 97-mph heater.
"Warming up, I was thinking I was going two [innings]," Madson said. "Once I knew definitely I was going back in the ninth after sitting down and calming down, the crowd definitely got me going. It felt good. I was surprised. They made some noise and made it easier to go back out there."
Astros shortstop Miguel Tejada went 1-for-5 to extend his hitting streak to 16 games, the longest active streak in the NL.