Yes, the Philadelphia Phillies are the NL East champions for the fourth consecutive year -- and Halladay is heading to the playoffs for the first time. Fittingly, the right-hander helped seal the deal.

Halladay allowed only two hits to earn his 21st win with his fourth shutout and ninth complete game -- all highs in the majors this season -- and Werth drove in four runs, leading the Phillies to a 8-0 victory over the Washington Nationals on Monday night, wrapping up the division with five games left.

"That's the reason you want to come to a team like this. They know how to do it," Halladay said, a bottle clutched in his hands. "It's the coolest thing I've been a part of. It's just the start, I think."

The Phillies have the league's best record and are assured of home-field advantage throughout the postseason -- the NL won the All-Star Game, remember -- although it's still uncertain which team they'll face next week in the division series.

Halladay (21-10) will be on the big stage of the playoffs for the first time in his 13th major league season, having played his entire career with the Toronto Blue Jays before being traded to Philadelphia last winter.

The Phillies let Halladay, catcher Brian Schneider and bench player Mike Sweeney pop the first champagne corks when they went to the clubhouse, because they are veterans who never have participated in the playoffs.

"I've watched it too much from the side," Halladay said, noting that he had seen such clinching parties on TV only, "so just glad to be a part of it."

Normally stoic on the mound, the 2003 AL Cy Young Award winner punched his glove with his pitching hand after striking out a swinging Danny Espinosa for the final out.

"I wanted him out there," Phillies manager Charlie Manuel said of letting Halladay go the distance. "I felt like he earned it, and he deserved it."

After the final out, Halladay instantly broke into a big smile, and the Phillies gathered in the middle of the diamond for hugs and high-fives. Thousands of red-clad, towel-waving Phillies fans in the announced crowd of 14,309 gave a standing ovation then began their last in a long series of chants of "Let's go, Phillies!"

"It was fun, but it's only going to get funner," Halladay said. "Honestly, it didn't matter who finished it, as long as we got it done."

Halladay's years without a postseason trip were tied for fourth-most among active players; the highest total on that list belongs to Sweeney, whose drought ends in his 16th season, STATS LLC said.

Werth homered, doubled and singled to back Halladay.

"Now we can put this behind us after we celebrate this tonight. We've got a long way to go. We've got a long road," Werth said. "We know where we want to be."

Completely undisturbed by a light rain that began falling in the third inning, Halladay gave up a single to Wilson Ramos in the third, and another to Adam Dunn in the eighth. But that was it. The pitcher nicknamed "Doc" didn't walk a batter and struck out six, including one to end each of the first three innings. He faced the minimum 21 batters through seven innings, because Ramos was erased when the next hitter, Alberto Gonzalez, grounded into a 4-6-3 double play.

The Phillies went ahead 1-0 on Werth's 26th homer, a drive off John Lannan (8-8) in the second inning. Lannan, in his final start of the season for the last-place Nationals, gave up four runs and seven hits in 5 2/3 innings.

Each hit for Philadelphia led to roars that must have made it feel like a home game for the Phillies. About 35 minutes before the first pitch, a loud cheer greeted Halladay as he walked toward the visitors' bullpen beyond left field, wearing a red warmup jacket with the temperature in the 70s.

Might as well have been Citizens Bank Park -- except a lot emptier in the stands.

"Kind of embarrassing when everyone in the stadium is clapping against you and you're at home," Nationals shortstop Ian Desmond said. "It's not really where you want to be."

The only moment when Halladay appeared ruffled in the least bit was in the ninth inning -- when he was at the plate. Nationals reliever Joe Bisenius threw a pitch that made Halladay duck and tumble in the batter's box, mussing his jersey with dirt. That prompted an expletive-filled chant from Phillies supporters.

Nothing was going to slow the Phillies on Monday, though, and they improved to 46-17 since July 21, when they trailed Atlanta by seven games. Eight days later, they traded for Roy Oswalt, adding him to Halladay and 2008 World Series MVP Cole Hamels for as fearsome a threesome of starting pitchers in the majors.

And what a stretch run: Philadelphia is 20-5 in September, its most wins in the season's final month since compiling 22 in 1983.

Looking to become the first team in 66 years to win three consecutive National League championships, the Phillies started this season strong, before injuries and an inconsistent offense took a toll. Six of Philadelphia's eight regulars spent time on the disabled list, and nearly all saw their production decline. At one point, Chase Utley, Ryan Howard and Shane Victorino were absent during a nearly two-week stretch in August.

Unlike previous years, when they counted on a potent offense, the Phillies relied on outstanding pitching in 2010. Led by Halladay, Hamels and Oswalt, the starting rotation dominated, especially in September. Still, it was a much tougher road to the postseason than a year ago, when Philadelphia moved into first place for good on May 30, before eventually losing to the New York Yankees in the World Series.

The Phillies wrapped things up against the Nationals in 2007 and 2008, too.

"For years to win the division, you had to go through Atlanta," Nationals manager Jim Riggleman said. "Now you've got to go through Philadelphia."

Having won the 2008 World Series for the franchise's second title, the Phillies are chasing another championship.

"This is what you play for. This is why you're here. If you're not here to try to win a championship, you're here for the wrong reasons. We've been through so much this year. We've had so many injuries and been able to battle through it," Howard said, a cigar in one hand and a can of beer in the other. "We feel like we kind of have some unfinished business and have taken the first step."

Game notes

Philadelphia SS Jimmy Rollins did not start the game because rain much of Monday left the outfield grass slick. Rollins pinch-hit on Sunday after sitting out 14 games with a tight right hamstring. ... Nationals 3B Ryan Zimmerman probably will miss the rest of the season because of an injured rib muscle on his right side.