WASHINGTON -- The first winning season in franchise history didn't thrill Washington Nationals manager Davey Johnson when he was reminded of it.

"I guess," Johnson said and paused. "I wasn't real concerned about it."

The Nationals, who moved to Washington for the 2005 season, had never won more than 81 games. After their 2-1 win over the Chicago Cubs on Monday, they have their 82nd victory, a 6½-game lead over Atlanta in the NL East and the best record in the majors.

"We haven't really done anything yet and we're looking for bigger things," Ryan Zimmerman said. "It not being a major story shows how far we've come."

Ross Detwiler allowed four hits in seven shutout innings and Adam LaRoche hit a second-inning homer for Washington. Detwiler (9-6) struck out three and walked three, allowing only one runner to get past second base.

"Today he was real special. He mixed in some breaking balls. Even the ones that were bad were pretty good," Johnson said.

Chicago right-hander Jeff Samardzija gave up a long home run to LaRoche to lead off the second. LaRoche's 25th home run landed in the front row of the second deck. It's the fourth time in his career LaRoche has hit 25 or more home runs.

Zimmerman's RBI double scored Bryce Harper in the eighth for the second run.

Drew Storen pitched a perfect eighth.

Tyler Clippard allowed two hits and a two-out RBI single to Welington Castillo in the ninth. Clippard threw the ball away for an error and allowed pinch-runner Tony Campana to reach second before striking out Josh Vitters for his 30th save in 33 opportunities.

Samardzija (8-13) allowed seven hits in seven innings. He walked one and struck out eight.

"You love playing against these kind of teams. When you're a team in our situation, anytime you can play these first or second-place teams where they're still playing for something, it means a lot, and they're fun games," Samardzija said.

Chicago, whose loss on Sunday guaranteed a third straight losing season, has dropped three straight. The Cubs have a 12-23 record in one-run games.

"It's amazing how you can be in so many games and never win them," manager Dale Sveum said. "That's a sign of a team that needs to get a long way before you start winning those games."

The Nationals went 81-81 in their first season in D.C., lost a combined 205 games in 2008-09, and finished 80-81 in 2011.

"We've come a long way. You can't start an organization from the ground up and expect that to happen real quickly," Zimmerman said. "Now, we're going to be set not just for this year, but for a lot of years to come. We have a long ways to go. It can get a lot better. You have to learn how to win and you have to learn how to do a lot of things right at this level to win."

Their 82nd win puts them 30 games over .500.

Detwiler recited the team's upcoming schedule, which includes three games against the second-place Braves in Atlanta Sept. 14-16.

"We know if we win the games there's no way we're out of it," Detwiler said.

Game notes

Johnson, GM Mike Rizzo and pitching coach Steve McCatty met with RHP Stephen Strasburg to explain the reasons the team is ending his season after two more starts. "I'm not sure any of us understand, but it's the right thing to do," Johnson said. ... Washington OF Michael Morse left the game in the fourth inning with a sore right thumb. "I knew their pitcher was going to pound him in. He didn't want to come out," Johnson said. Johnson expects him to play on Tuesday. ... Nationals LHP Sean Burnett will probably miss a few days with a sore right elbow, Johnson said. ... Washington purchased the contracts of RHP Christian Garcia and LHP Zach Duke from Triple-A Syracuse. RHP Henry Rodriguez was moved to the 60-day disabled list. ... U.S. Olympic swimming gold medalist Katie Ledecky threw out the first pitch. ... Nationals RHP Edwin Jackson (8-9, 3.53) and LHP Chris Rusin (0-1, 1.80) are Tuesday's pitchers. Rusin and three others, RHPs Jaye Chapman and Rafael Dolis and C Anthony Recker, will be added to Chicago's roster on Tuesday.