Outfielder Jason Heyward and the Braves lost their grip on a postseason berth last season. (Curtis Compton/Associated Press)

The Atlanta Braves have the third-best winning percentage in the major leagues since the all-star break (24-12, .667) and they have become so confident in their array of starting pitchers that they are employing a six-man rotation through the end of August.

Yet, the Braves open a three-game series with the Washington Nationals on Monday night under some stress. After losing two of three games to the Dodgers — the first series it has lost since mid-July — Atlanta is five games back of Washington in the National League East. Lose two out of three to the Nats this week and the margin is six games, a wide moat when you consider Washington is the second-hottest team in baseball behind the Reds.

This is the reward for playing sizzling baseball for five weeks?

“Six games is a large margin when you are talking about a team as good as Washington,” said Chipper Jones, the Braves’ veteran third baseman who is retiring following this season. “They just don’t lose a lot of games in a row and they don’t make that many mistakes.

“If we dig ourselves that big a hole we’re going to be focusing more on the wild card than the division and that’s the last thing I want to do as a player to look in the rearview mirror and guys chasing us from behind. We all know how that ended last year. We need to set our sights on the top.”

What happened in 2011 was a disastrous tumble. The Braves owned a 101 / 2-game lead in the wild card over St. Louis on Aug. 26, but went 9-18 in September and were nosed out of the playoffs by the Cardinals.

When asked if the Braves (70-51) might resort to disaster planning and replaying the 2011 collapse if the Nationals leave them behind this week, Jones said, “We learned a valuable lesson, we’ve got to close things out.”

Atlanta lost to the Dodgers, 5-0, on Sunday, collecting just three hits. The Braves hit .178 in the three-game series, which was particularly stressful for catcher Brian McCann, the six-time all-star, who has just four hits in his last 39 at-bats. Second baseman Dan Uggla, who had pulled out of his tortuous two-month slump in early August, is in a tailspin again with three hits in his last 27 at-bats.

“I see guys with that look on their face, you know at the plate, they’re scuffling,” Jones said. “We got to get them going.”

What’s going for Atlanta is pitching, the hallmark of a franchise that went to the playoffs continuously from 1991 to 2005. The Braves have the hottest half of their atypical six-man rotation lined up for the Washington series. In two of his three starts this month, Tim Hudson (12-4), the Monday night starter, has not allowed an earned run. Paul Maholm (11-7), the starter on Tuesday, has allowed one earned run his last two starts, and Kris Medlen (4-1), the starter on Wednesday, is coming off a shutout of the San Diego Padreslast Thursday. The Braves have won the last 15 games in which Medlen has started.

The Braves’ ERA against the Nationals in 12 games is 5.13, which is the highest ERA against any National League opponent, but Hudson said Atlanta’s pitching has been improved since those first 12 games of the season against Washington.

“When we played those guys earlier in the year, I don’t know if we’re playing much better now, but I know we’re pitching a lot better,” Hudson said. “That’s been our Achilles’ heel against them; we haven’t pitched that well against those guys. That can be lack of execution of our pitches, but also the improvement of their offense this year.”

But it is not just the Nationals hitters the Braves have struggled with, it’s their pitchers, too. Atlanta is hitting .239 against Washington in the 12 games and .255 in all games. The Nationals have won 8 of 12 games between the teams this season.

Atlanta’s starters better be sharp because the Braves will be working with one less reliever in the bullpen in Washington.

“Our pitchers are rested and feeling better,” said left fielder Martin Prado. “The pen is going to be short; we just hoping those guys pitch well and we don’t have to use the pen so much. But so far, they have pitched well with what we are doing.”

Prado relishes the idea of playing in a cauldron in Nationals Park in front of a huge crowd.

The Braves can immediately close the gap with the first-place team in the division, or they can be left behind and tossed into the wild-card fray in September.

“We play for the challenge and the pressure,” Prado said. “It’s going to be like winter ball with the noise and intensity. It’s what you want, it’s why you play.”