PHOENIX -- Dan Haren picked up where Brandon Webb left off.
Haren (6-4) helped the Diamondbacks post back-to-back shutouts for the first time since May 26-27, 2006, at Cincinnati. Webb beat the Nationals 4-0 on Saturday to snap Arizona's five-game losing streak.
"'Webby' came out yesterday and did what an ace is supposed to do," Haren said. "He came out and set the tone."
Orlando Hudson's three-run homer, his second in three days and sixth of the season, gave Haren all the support he would need in the first inning. Haren gave up four hits, walked three and struck out five.
"I'm happy with the way I threw the ball," said Haren, who relied on his curveball to keep the Nationals off stride. "I'm more happy with the way the team has played the last couple days."
Relievers Chad Qualls and Tony Pena each got three outs to finish off the four-hitter.
This is exactly what the Diamondbacks expected when they acquired Haren from Oakland in a trade last winter, giving their rotation a formidable 1-2 punch.
"You try to get your two horses up there," Arizona manager Bob Melvin. "We feel good about all five (starters), but obviously you want your innings-eaters up there at the top, your two horses.
"Those two days, you want to give the bullpen a little bit of a break, knowing that they're going to give you some innings and performances similar to what we've seen the last two nights."
Webb leads the staff with 83 2/3 innings. Haren is second with 76.
Haren gave up a leadoff single to Felipe Lopez in the first, then didn't allow a hit until Jesus Flores' double in the fourth. The Nationals never reached third.
"(Haren) made us play catch-up baseball from the get-go, and the way we're swinging the bats, it's not a good thing," said Washington manager Manny Acta, whose team wrapped up a 2-4 trip out West. "Having a guy like Haren in front of you made it very tough."
Chad Tracy added a solo homer for the Diamondbacks, who salvaged the final two games of a six-game homestand.
The Diamondbacks were relieved to see June arrive. They went 11-17 in May but lost only a half-game of their lead in the feeble NL West, where every other team entered Sunday with a losing record.
Arizona left after the game for a 10-game trip to Milwaukee, Pittsburgh and the New York Mets. It's a big test for a team that is 11-13 on the road and 10-16 against the NL East and Central.
"I think we've gotten back to being a little more confident these last couple days, and hopefully we'll go out and play well in Milwaukee and take care of business from there," Haren said. "This team is too good to not be able to win on the road, so I don't think anyone is worried."
The Diamondbacks jumped on Shawn Hill (0-2) in the first. After leadoff man Stephen Drew and Chris Young singled, Hudson lined a 1-1 pitch 385 feet over the right-field fence.
"Three batters in, three runs down," Hill said. "That's my fault entirely, so it's completely unacceptable."
The Diamondbacks made it 4-0 in the second. Chris Snyder doubled, moved up on a groundout and scored on a wild pitch by Hill.
Tracy went deep in the third, his first.
Hill went four innings, his shortest outing of the season, allowing five runs and seven hits. He walked one and struck out three.
"Didn't do a good job of keeping the team in the ballgame, basically," Hill said.
Arizona RF Justin Upton was a late scratch with flu symptoms. ... Arizona 1B Conor Jackson is expected to miss three to five days with a strained right quad, but manager Bob Melvin said Jackson could be available to pinch hit. ... Washington RHP Jason Bergmann's eight-inning complete game on Saturday night was the Nationals' first since Aug. 15, 2006. The 261 games between complete games was the major leagues' longest drought.