WASHINGTON » Roy Halladay stood in the middle of the sort of wild clubhouse celebration he’d longed to be a part of for so many years, a pair of goggles perched on the brim of his dark cap with "Playoffs" written in white above a red Phillies "P."

Rookie mistake, putting those goggles up there, instead of over his eyes: Halladay scrunched his face and braced against the sting as teammate Jayson Werth poured a full bottle of bubbly over him.

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 an 8-0 victory over the Washington Nationals last 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."