Roy Oswalt threw eight shutout innings and delivered his first RBI of the season, part of an 11-hit attack that helped Houston beat Washington 3-2 Thursday night for the Astros' season-high fifth straight road victory.
"We have made up a lot of ground since the All-Star break," said Oswalt, the winner in seven of his past eight starts. "You have to win ... on the road. That is the biggest thing."
Washington, meanwhile, has lost 11 of 15, and it dropped into a first-place tie in the NL East with the idle Atlanta Braves. The Nationals led by 5½ games on July 3.
"What we're going to have to do," Nationals manager Frank Robinson said, "is get this thing going before we fall too far behind."
Oswalt (13-8) gave up six hits -- three times allowing two in an inning. But he was best in the clutch, getting the Nationals to go 0-for-3 with runners in scoring position and to ground into three double plays.
He also hit two batters, but struck out six without giving up a walk. Oswalt threw 77 of 93 pitches for strikes.
"He got stronger as the game went on," manager Phil Garner said. "I thought the key tonight was he pounded the strike zone. I don't think it was luck that they hit into double plays."
Brad Lidge gave up Preston Wilson's 17th homer, a two-run shot on a 3-2 pitch with one out in the ninth, before finishing the game for his 22nd save. That made this Washington's sixth straight loss in a one-run game.
It was the latest poor showing by a Nationals offense that has scored more than four runs just once in its last 10 games, averaging 2.9 runs in that span. Washington has lost eight of those games.
"Things are going bad," first baseman Brad Wilkerson said. "They keep swamping on us right now."
The home clubhouse was mostly empty and quiet after the game, the only sound the whirr of a fan. The stereo and TV were off. And there's more bad news for the Nationals.
They face Roger Clemens on Friday, and outfielder Jose Guillen -- whose 19 homers and 54 RBIs lead the Nationals -- said he might get a cortisone shot, which possibly could cause him to miss time.
Guillen has been battling shoulder, rib and foot injuries, all on his left side.
"The last three days, my bat -- I don't know where it's been," Guillen said after going 0-for-4 a second game in a row. "I've been swinging like a little kid."
The Astros, meanwhile, are making a run similar to the one that carried them to a wild-card berth last year.
On May 24, Houston was 15-30, but it has the majors' best record since that date. And despite losing their first three games after the break, the Astros have now won 12 of 16.
"If we pick up a game a week, we will be in good shape," Garner said. "You keep picking away."
Nationals starter Esteban Loaiza (6-6) went seven innings, allowing three runs -- two earned.
Everyone in the Astros' starting lineup except Lance Berkman had at least one hit, including Oswalt's RBI single in the sixth. Willy Tavares, Craig Biggio and Adam Everett each had two hits.
In the fifth, Houston scored an unearned run to lead 1-0. Everett and Brad Ausmus singled, and Oswalt bunted, trying to sacrifice over the runners. Wilkerson grabbed the chopper, but his throw glanced off fill-in third baseman Carlos Baerga's glove for an error, allowing Everett to score.
Mike Lamb's fourth homer, a solo shot to right leading off the sixth, made it 2-0. Later in that inning, Everett singled, stole second, and Oswalt drove him home.
It was on the mound, though, where Oswalt truly excelled.
"Roy did an incredible job again for us," Morgan Ensberg said.
Nationals INF Jamey Carroll made a diving stop of Everett's hard shot in the eighth and threw him out. ... The crowd of 36,840 booed loudly when SS Cristian Guzman batted in the eighth. Guzman, hitting .189 before the game, was benched this week.