The Washington Nationals and Atlanta Braves may well meet again next month, with the stakes higher, the pressure thicker and the air colder. For those who have not watched a team from Washington in a playoff baseball game in 79 years, Friday night offered a preview. The starting pitchers dueled, the managers played chess and 41,797 tomahawk-chopping souls jammed into Turner Field. The calendar said September. The field screamed October.

The Nationals will remain in firm control of the National League East no matter what transpires this weekend. But the Braves’ walk-off, 2-1 victory Friday night still gave the Nationals something to think about, even before Andrelton Simmons slid home and shortstop Ian Desmond’s wayward, desperate throw home bounded to the backstop.

The Nationals left the field spent, not discouraged. “No one in here is hanging their head,” Desmond said. “More scratching their head than anything.” They had played a knock-out, drag-out, whale of a game, and they knew more like it would be coming.

“This is playoff baseball,” right fielder Jayson Werth said. “Every team we play the rest of the way is in the hunt and hungry. These are the type of games we’re going to play for the next six weeks.”

The Nationals’ loss did little to endanger their chances to win the East. They still own a commanding edge, down from 81 / 2 games to 71 / 2, with 18 to play. “You play all season to build up that lead,” Werth said. They have two more chances to stifle the second-place Braves’ hopes this weekend. The Nationals could squander the division only by making a special kind of mess.

But if these teams meet again in October, in a playoff series short enough for one pitcher to take by the throat, they will know the Braves have one capable. The Nationals — Bryce Harper excepted — will need to figure out a way to beat Kris Medlen.

Friday night, Medlen dueled Ross Detwiler and, for the second time in a month, left the Nationals mystified by his sinking, cutting array of pitches. On Aug. 22 at Nationals Park, he held Washington scoreless for seven innings. Friday night, he may have been even better. Medlen struck out 13 in seven innings while allowing five hits and a walk. His eight looking strikeouts were the most by any pitcher in a game this season.

Only Harper’s home run in the sixth inning, a rope into the left field seats, tied the game and kept it making knuckles white into the ninth inning.

The ninth started with the final managerial gambit in a night packed with them. Drew Storen had ended the eighth inning, and he stood on the mound to start the ninth. When Braves Manaer Fredi Gonzalez sent left-hander Lyle Overbay to pinch-hit, Nationals Manager Davey Johnson responded by calling on Sean Burnett.

Burnett recorded the first out on a marvelous play by Desmond, who ranged deep into the hole and made a leaping, off-balance throw to first. From there, “they kind of bled us to death,” Werth said.

Simmons rolled a groundball single to Desmond. Michael Bourn, an in-game replacement, smoked a single to right, sending Simmons to third. The Nationals drew in the infield, and pinch hitter Tyler Pastornicky hit a grounder to Desmond. Simmons sprinted on contact.

Desmond fired home, but the throw skipped past catcher Kurt Suzuki and the Braves poured out of their dugout. Desmond received an error, but he believed he had to rush to make an improbable play.

“I’ve got a prayer, basically, with Andrelton Simmons at third,” Desmond said. “Just tried to get it as quick as I could and get rid of it. If I set, he’s already sliding in celebrating. There was a probably 1 in 10 chance, and didn’t get him.”

Detwiler did not dominate like Medlen, but he produced the same result with more turbulence. He used more curveballs than in recent starts after working on the pitch with coach Steve McCatty.

Detwiler yielded seven hits and a walk and allowed a runner into scoring position in four of his six innings. He still managed to hold the Braves to one run, which came on a fourth-inning sacrifice fly, striking out five and stranding seven.

“Det showed me something,” Johnson said.

After five innings, Medlen had struck out 10 and allowed three hits. Only Harper had solved him, ripping a line-drive single in his first at-bat and walking in the next. When Harper led off the sixth, Medlen tried something new against him, a first-pitch curveball. He hung the pitch, and Harper was ready for it.

Harper unleashed a violent swing, but under control. The ball seared off his bat, but he had stayed back long enough, keeping his front shoulder closed, to send the breaking ball to the opposite field. He had also hit under the ball enough for it soar about eight rows deep.

Harper sprinted around the bases, a 19-year-old with 19 home runs. He had tied the score at 1. When Harper returned to the dugout, sticking to recent custom when any hitter bashes a home run, his teammates showered him with still-wrapped Dubble Bubble.

“I was just trying go up there, have some good at-bats against him,” Harper said. “He’s a great pitcher. He was pretty effective out there mixing things up. I’m just tying to put something in play.”

With help from a crucial, wall-banging catch by left fielder Roger Bernadina, the Nationals kept the Braves scoreless until the ninth. But the Braves’ lockdown bullpen stymied the Nationals. In the ninth, Craig Kimbrel struck out all three hitters he faced on 10 pitches. The Braves may not have gotten back into the race, but they sent a message.

The Braves may not have gotten back into the race, but they sent a message. The Nationals feel prepared to respond.

“We’re going to be tested,” Werth said. “But I think we’re ready for that test. Probably the last two weeks, I could really tell a difference in this team. We’re a championship-caliber ball club. A lot of guys just hitting [their] stride. I like where we’re at.”