Houston, which has a one-game lead over Florida in the NL wild-card race, won its 12th straight over Philadelphia. The free-falling Phillies fell 2½ games behind with their fifth straight loss.
"That's the first time I've ever faced Billy," Biggio said of his close friend and teammate for eight years in Houston. "He threw me a fastball in, then inside again. The last pitch was 99 mph, so I could have popped it up."
Wagner (4-3) retired the first two batters in the ninth before Jose Vizcaino reached on third baseman David Bell's fielding error. Willy Taveras beat out an infield single to shortstop, and Biggio followed with a drive into the left-field seats for his 20th homer.
"I tried to get it up, but that's his zone," Wagner said. "You have to make sure it's up enough."
Making matters worse for Philadelphia's All-Star closer, Biggio just signed a jersey for Wagner's son.
"Here you go, son, here's a jersey from the guy who just homered off your dad," said Wagner, who got the loss for the second straight game after not facing Houston the first nine times the teams met since he was traded to Philadelphia in 2003.
The Phillies rallied in the eighth against Dan Wheeler. Pinch-hitter Jason Michaels walked to start the inning. After Chase Utley sent Taveras to the center-field wall on a flyout, Abreu hit a drive deep into the Phillies' bullpen in center field to tie it at 5. The normally low-key Abreu shouted at his teammates in the dugout on his way to first base and slowly jogged around the bases.
Qualls entered and got pinch-hitter Michael Tucker on a grounder to first base that forced Chavez at the plate. But Victorino lined the next pitch to right to score Howard. Bell was thrown out at the plate by right fielder Jason Lane.
It was Victorino's first hit in the majors since May 14, 2003.
Despite the Phillies being in the playoff chase, only 29,026 turned out at Citizens Bank Park. Most fans spent the first seven innings voicing their displeasure with the Phillies. They booed manager Charlie Manuel when he walked out to the mound for a pitching change, chanted "E-A-G-L-E-S" randomly throughout the game and jeered whoever failed to deliver in clutch spots.
Abreu got a standing ovation when he came through in a crucial spot, but the team left the field to a chorus of boos.
"This is a hard loss," Manuel said. "We had it and we gave it away. We have to get our act together and start winning games."
Before connecting off Vicente Padilla in the sixth, Lamb was hitting just .208. He hadn't gone deep since Aug. 2.
Berkman walked to start the inning and went to third on Lane's double. Lamb then lined a 2-2 pitch into the right-field seats for his eighth homer, giving Houston a 5-3 lead.
Padilla allowed five runs and seven hits in 5 1/3 innings, one of his poorest outings since the All-Star break. The right-hander has been Philadelphia's most consistent starter since early July. Since nearly being pulled from the rotation and almost losing his roster spot after starting 3-8 with a 6.69 ERA, Padilla was 5-4 with a 2.60 ERA in his previous 11 starts.
Howard gave the Phillies a 2-1 lead in the second on his 15th homer, a liner into the seats in right-center field. The slugging first baseman filling in for the injured Jim Thome leads NL rookies with 15 homers, even though he spent most of the first three months in Triple-A.
Utley's fielder's choice grounder scored Jimmy Rollins to make it 3-1 in the third.
Berkman gave the Astros a 1-0 lead in the second with his 18th homer and fifth in seven games. Houston cut it to 3-2 in the fourth on a fielder's choice grounder by Adam Everett.
Brandon Backe, making his first start since July 23 after being sidelined with a strained left ribcage, allowed three runs and three hits in four innings.
"Wagner's tough. We all know how good he is," Astros manager Phil Garner said. "We just buckled down."
- Astros 3B Morgan Ensberg missed his second straight game with a bruised hand. He was hit by a pitch Monday night.
- Rollins extended his career-best hitting streak to 14 games.
- Thome spent a few innings in the Phillies' television broadcast booth. He plans to return to Florida to after this 10-game homestand concludes next week.