PHILADELPHIA -- With the best record in baseball, the Phillies can win without extra help.
The sloppy Washington National had no chance Saturday night.
Oswalt (5-7), making his second start since coming off the 15-day DL Aug. 6 with a back injury, gave up three runs on six hits in seven innings. He allowed a career-high 12 hits in a 3-1 loss at San Francisco on Aug. 7.
This time he was much sharper although he didn't have to be too fine thanks partly to Washington's shoddy fielding, as the Nationals committed three costly errors that led to seven runs.
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"That's a good ballclub," Nationals manager Davey Johnson said. "You can't give them extra outs and that's what we did tonight."
"You get those extra opportunities and you definitely want to cash in on it," Howard said, "because you know that's gonna take some of the air out of them."
Howard continued his hot streak which has coincided with the Phillies' acquisition of Hunter Pence, who bats fifth behind Howard. In 14 games with since the deal with Houston, Howard is batting .333 (18-for-54) with six homers and 17 RBI.
"He's definitely watching the ball better and getting better pitches to hit by being a little more patient," Phillies manager Charlie Manuel said. "And if he feels like Hunter being in our lineup has helped him, then more than likely it's helped him."
Said Howard, "I feel like the lineup is great right now. It's just a matter of continuing to do what we're doing and we're having a lot of fun."
Howard's two-out, two-run homer in the first inning put Philadelphia up 2-0 and gave Oswalt a cushion. The Nationals scored two in the second, but Oswalt settled down after that and finished with five strikeouts and just one walk.
"I felt pretty well tonight," Oswalt said. "I felt really good with my offspeed stuff. Overally my fastball is coming back and I feel healthy. It's just a matter of getting out there, getting strength and durability, that's the biggest thing."
John Lannan (8-8) surrendered seven runs, but just one earned run, in three innings on four hits while walking five and striking out one. He did not come out to pitch the fourth. He said he "aggravated" his knee on a play in the third, but Johnson said he wasn't removed due to injury.
"I said I could go but they wanted to make a change," Lannan said.
Lannan appeared to hurt himself on a play in a wacky third inning when the Phillies scored five runs, but just one that was earned. With the bases loaded, Wilson Valdez hit a chopper in front of the plate. Lannan charged and dived for the ball, retrieving it and in one motion scooping it to catcher Wilson Ramos for a force out at the plate.
He got up slowly and stayed in the game to face three more batters, but did not come out for the fourth.
Lannan's struggles against the Phillies continued, as he dropped to 1-11 with a 5.84 ERA lifetime in 15 starts against Philadelphia.
Washington's Michael Morse, who sat out Friday's game after being hit on the elbow by Chicago's Ryan Dempster Thursday, returned to the lineup and went 2 for 4 with a double and an RBI for the Nationals.
Washington's troubles in the third started when Ian Desmond threw high to first on Shane Victorino's grounder to lead off the inning. Chase Utley followed with a seeing-eye base hit up the middle to put runners on first and third. Howard then singled home Victorino and Utley scored on Raul Ibanez's groundout. With Howard on third and the bases loaded, Lannan got the second out on the force at home.
Lannan then walked Oswalt with the bases loaded to allow another run to score, and the Phillies scored two more when Jimmy Rollins hit an infield single that scored Carlos Ruiz and also Valdez, who reached from second ahead of the throw of second baseman Danny Espinosa to make it 7-3 Philadelphia.
The Phillies tacked on another unearned run in the sixth off reliever Collin Balester.
Rollins reached on a wild pitch on the third strike and, after Victorino singled, Morse booted Utley's grounder to load the bases. Howard grounded to first for a possible double play, but Ballester dropped the return throw from Desmond to allow Rollins to score and make it 8-3 Phillies.
Howard's homer put the Phillies up 2-0, although both runs were unearned after Espinosa began the game with an error on Rollins' grounder.
The Nationals responded with a pair of runs in the top of the second, on RBI hits by Laynce Nix and Desmond.
Oswalt retired 10 of the next 11 batters.
The Phillies tacked on three runs in the eighth on RBI hits by Hunter Pence and Ruiz, and Ibanez's sacrifice fly.
Zimmerman went 1 for 4 one day after going 0-for-2 to snap his 19-game hitting streak. Werth, who left Philadelphia to sign a seven-year, $126 million deal with the Nats this offseason, went 1 for 3 with a walk and once again received boos during each at-bat. The Phillies honored several former players in a pregame ceremony, including Hall of Famers Mike Schmidt and Steve Carlton. The Phillies' crowd of 45,570 was the club's 184th consecutive home sellout. Phillies right-hander Roy Halladay (15-4, 2.51) is scheduled to face Washington right-hander Chien-Ming Wang (1-2, 3.60) in Sunday's series finale. Halladay is 3-0 with a 3.13 ERA in three starts against the Nationals this season, and 11-1 with a 2.21 in his career against Washington. Wang, who missed more than two years following shoulder surgery, will be making his fourth start of the season. He picked up his first win since June 28, 2009 last Tuesday against the Cubs, when he pitched six scoreless innings and allowed just one hit. Wang combined to win 38 games in 2006 and '07 for the Yankees.