ATLANTA >> The Washington Nationals bounced up and down in unison near second base, not bothered at all by a smattering of boos from the crowd at Turner Field.

They were saving the real celebration for the clubhouse.

The Nationals wrapped up their second NL East title in three years against the team that knocked them out of the top spot last season, beating the Atlanta Braves 3-0 on Tuesday night.

Tanner Roark pitched five-hit ball over seven innings and Ian Desmond’s two-run homer broke a scoreless tie in the sixth, sending Washington back to the playoffs with nearly two weeks to spare.

“Nice to have it done,” said Washington first baseman Adam LaRoche, who began his career with the Braves. “The sooner, the better.”

In the clubhouse, the Nationals drenched each other — and pretty much anything that moved — with seemingly endless streams of beer. Lil Jon’s party anthem “Turn Down For What” boomed from the speakers. Bryce Harper, wearing goggles and a fire helmet with “34” across the front, posed for selfies with his teammates.

“We want to keep going, keep winning ballgames,” Harper said.

The clinching victory was especially sweet coming against the Braves, who finished 10 games ahead of the Nationals in 2013. The roles were reversed this season as Washington steadily pulled away down the stretch.

The teams were tied for the lead as late as July 20.

It was no contest the rest of the way. The Nationals stretched the lead to a season-high 12 1/2 games with the victory.

“It’s just one step. There’s a long, hard road ahead of us,” Nationals outfielder Jayson Werth said. “But we’re going to enjoy the moment for now.”

Atlanta lost for the 11th time in 14 games, further damaging its hopes of making a third straight playoff appearance, this time as a wild card. The Braves dropped to 75-76 with their fifth straight loss, the first time they have been under .500 since losing on opening day.

“You never want anybody to celebrate on your field,” manager Fredi Gonzalez said. “But they did it professionally, I thought. I didn’t expect anything less from that organization.”

The Braves fell 5 1/2 games behind Pittsburgh for the second NL wild card with 11 games left in the regular season.

“We’ve still got a chance,” Gonzalez insisted. “Now we’ve got to set our sights on a winning streak and maybe we can come in with a second wild card.”

Roark (14-10) pitched around four leadoff singles by Atlanta, which never got a runner past second base. He struck out four and walked none, lifted after throwing 89 pitches. Tyler Clippard worked a scoreless eighth, and Drew Storen finished up for his seventh save.

The Nationals finally broke through in the sixth against Aaron Harang (11-11). After Werth led off with a walk, LaRoche took a called third strike before Harang worked the count to 2-2 on Desmond.

The next pitch was a breaking ball that stayed up in the zone. Desmond got all of it, sending a drive deep into the left-field seats for his 23rd homer. Left fielder Justin Upton barely moved, while Harang pumped his fist angrily on the mound.

“A curveball down the middle,” Desmond said. “It ended up going out of the ballpark.”

He scored Washington’s other run in the ninth, trotting home on David Carpenter’s wild pitch.

The Nationals will be making just the third playoff appearance in the franchise’s 46-year history. The club reached the postseason only once as the Montreal Expos (in 1981) before moving to Washington for the 2005 season.

Two years ago, the Nationals had a major league-leading 98 wins but were stunned by the St. Louis Cardinals in the deciding game of the NL division series. Washington jumped ahead 6-0 after three innings and still led 7-5 going to the ninth, only to give up four runs with two outs.

“We have a chance for redemption,” LaRoche said.

TRAINER’S ROOM

Nationals: Harper was back in the lineup after leaving Monday’s game in the third inning when he felt light-headed. Manager Matt Williams said Harper had a “little bit of the gunk” that seemed to be going around in the Washington clubhouse.

Braves: C Evan Gattis missed his eighth straight game since coming down with strep throat. Gonzalez said he doesn’t know when Gattis will be healthy enough to return.

UP NEXT

Nationals: LHP Gio Gonzalez (8-10) has won two of his three starts in September after going nearly two months without a win.

Braves: LHP Alex Wood (10-10) has lasted at least seven innings and allowed two runs or fewer in 12 of his 22 starts. Atlanta is 5-7 in those games.

A TRADITION LIKE NO OTHER

It was the 10th time the Braves have watched a visiting team celebrate a playoff victory or postseason-clinching win since moving to Turner Field in 1997.