"What's the big deal?" Johnson joked.
The Nationals used Ross Detwiler's six strong innings and Ryan Zimmerman's RBI double to lock up a playoff spot Thursday night with a 4-1 win over the Los Angeles Dodgers.
"Nats Clinch" flashed on the scoreboard as Washington ensured at least an NL wild-card spot, delighting the crowd of 30,359.
"That was fun, but it's not what I had my eye on," Johnson said. "I don't want this."
The fans stood and cheered in the ninth inning, then got even louder when Drew Storen struck out Hanley Ramirez to end it. Johnson saluted the crowd as he left the field and the team wore caps and T-shirts acknowledging the playoff berth.
"I noticed like in the fifth or sixth, some signs, some different things that kind of keyed me into that this wasn't going to be an ordinary evening," Jayson Werth said.
"That was not an ordinary win."
Nineteen-year-old centre fielder Bryce Harper claimed ignorance of the team's situation.
"Everyone's going crazy. I looked at the fireworks and I go: 'I guess we just did something.' Then somebody handed me the playoff shirt and playoff hat and I said, 'Well, I guess we're going to the playoffs,'" Harper said.
Washington's magic number to win the NL East was reduced to eight. The Nationals lead idle Atlanta by 5 1/2 games.
"We've been through a lot and a lot of us in here have been through a lot of not-good times and these are the beginning of hope for a lot of good times," Zimmerman said.
Zimmerman is the only Nationals player to appear in each of the team's eight seasons.
"It's a first step, and it's a long ways to go," he said.
The Nationals became the second team in the majors to clinch a playoff spot this year. Cincinnati sealed its slot earlier in the day.
They celebrated with a private champagne toast. No spraying and no protective plastic over their lockers.
"I think there was some talk about not celebrating at all, but I kind of talked them out of that," Werth said.
"The next one would not be as subdued, I would imagine," Zimmerman said.
Washington was last in the post-season 79 years ago, when player-manager Joe Cronin and the Senators lost to the New York Giants in five games in the World Series.
"I can't remember that year," Johnson said with a laugh.
Until this year, the Nationals had never had a winning season — nor finished above third place — since moving from Montreal for the 2005 season. It will be just the franchise's second post-season berth and its first since the Expos came within a game of the World Series in 1981.
The Nationals lost more than 100 games in both 2008 and 2009, allowing them to draft pitcher Stephen Strasburg and Harper.
The loss dropped the Dodgers three games behind St. Louis for the NL's second wild-card spot. Milwaukee moved ahead of Los Angeles with its win over Pittsburgh.
Manager Don Mattingly agreed the team's playoff chances dimmed after the Dodgers' 10th loss in 14 games.
"You know, honestly, it does. It feels like it is a little bit, and I don't think there's any way for us to look at it other than that," he said. "I mean, it's, yeah, we're going the wrong direction.
"For us at this point, we're going to have to put a run together that's going to be more than just win a series."
Detwiler (10-6) allowed just Mark Ellis' fourth-inning home run and two singles. Storen pitched the ninth for his third save.
Zimmerman's third-inning double scored Harper with Washington's first run. Zimmerman then took third on an infield out and scored on a wild pitch by Chris Capuano (11-11).
The Nationals added two runs in the fourth on a walk to Ian Desmond, an RBI double by Danny Espinosa and a sacrifice fly by Kurt Suzuki.
Werth, who signed a $126 million, seven-year deal with the Nationals before the 2011 season, is most eager for the post-season to begin.
"I've got a lot to prove. I've got a lot of people to prove wrong, and I can't wait," Werth said.
NOTES: Mattingly said that LHP Clayton Kershaw was continuing with his throwing program. Kershaw will have to demonstrate he's free from pain in his right hip before he'll be able to pitch again, the manager said. ... Johnson said RHP Chien-Ming Wang will start on Sunday. Wang hasn't started since June 19. He missed nearly two months with a right hip injury.