HOUSTON -- Mike Lamb is doing everything he can to break into Houston's regular lineup. Maybe this performance will finally earn him a spot.
Lamb's 3-for-5 night boosted his average to .419, enough to raise the question why he hasn't replaced Morgan Ensberg in the everyday lineup. Ensberg is batting .219.
"I can't change their plans for the lineup," Lamb said. "I can only do my job when I get in there. I can't go in there and fight them or anything. I can only do what I can do."
Houston manager Phil Garner wouldn't speculate on whether Lamb might've won more playing time.
"Lamb's doing a nice job, a very nice job," Garner said, without elaborating.
Oswalt (6-2) beat Arizona for the sixth time in seven career starts, allowing three runs and eight hits in six innings. The Astros ace struck out seven and has won 24 of his last 30 starts at Minute Maid Park.
Oswalt admitted he didn't pitch his best. Thanks to the Astros' offense, he didn't have to.
Pence had a solo homer and a two-run double and Carlos Lee also had a solo drive for the Astros, who finished with 14 hits.
"The guys swung the bat well today," Oswalt said.
Arizona starter Livan Hernandez (3-2), 5-1 in his last six outings in Houston, lasted only four innings in this one, surrendering eight runs and 11 hits, both season highs.
Arizona jumped out to a 2-0 lead in the first inning against Oswalt, who'd allowed one run or less three times in his six previous starts against the Diamondbacks.
Houston native Chris Young and Eric Byrnes singled before Oswalt fanned Orlando Hudson for the first out. Chad Tracy then walked and Tony Clark followed with a two-run double down the left-field line.
Lamb hit a 2-1 pitch from Hernandez over the right-field wall in the bottom half for his second homer of the season. Lamb singled and scored in the third and fourth innings as the Astros blew the game open.
Lamb said he's tinkered with the mechanics of his swing, but can't otherwise explain his hot start. But if he's upset about not playing more, he's not showing it.
"Every player wants to play and gets frustrated at not playing," he said. "The thing you have to be careful with is not letting it affect the other guys on the team.
"I know what I can do and I've been doing what I can do," he said. "If that's not good enough, I'll do the best to help the team in any way I can. I still have a job, so I can't complain too much."
Lamb's first single put runners on first and third and Lance Berkman walked to load the bases with no outs. Hernandez struck out Lee and Scott, but Pence dropped a blooper in front of Young in center field for a two-run double.
The two RBI were Pence's fifth and sixth with the bases loaded this season -- he hit a grand slam in St. Louis on May 5.
Young hit a run-scoring single in the fourth to tie it at 3.
But Hernandez got into trouble again in the bottom half. Brad Ausmus hit a leadoff double and Lamb followed with a sharp grounder that skipped past Tracy at third and put Houston in front 4-3. Berkman then singled for Houston's ninth hit, the most allowed by Hernandez in eight starts this season.
Arizona manager Bob Melvin didn't think Hernandez pitched as badly as his numbers suggest.
"He gave up some runs and it put a little pressure on him," Melvin said. "Maybe I needed to get him before I did. One of those hits just slips through and then the floodgates opened."
Lee atoned for his bases-loaded strikeout in the third with a single that scored Lamb and stretched the Astros' lead to 5-3. Scott then cleared the bases with a drive into the upper deck in right field, his fourth homer of the season.
Lee and Pence homered in the seventh off reliever Brandon Medders. Lee leads the NL with 34 RBI.
- Hernandez had his shortest outing since July 6, 2006, when he played for Washington and lasted only 1 2/3 innings in a loss to the Florida Marlins.
- Houston 2B Craig Biggio's 647th career double was his 2,964th career hit. Biggio is seventh on the career doubles list, 10 behind Nap Lajoie. The hit moved Biggio into a tie with Sam Crawford for 28th on the career list.
- Stephen Drew doubled in the eighth off Houston reliever Brad Lidge and later scored on a passed ball.