With the game tied at 2 and bases loaded, Desmond hit a 2-1 pitch from Atlanta left-hander Jonny Venters up the middle to score Willie Harris and Danny Espinosa.
Before his game-winning hit, Desmond vowed that he was not going to draw a walk and let the next hitter, Adam Dunn, try to do the damage. Desmond remembered what happened the previous day during Washington's 5-0 loss. He walked in the seventh against Venters and Dunn struck out to end the inning.
"That left Dunn in a tough situation -- lefty/lefty," Desmond said. "Venters is pretty good on lefties. I wanted to make sure that I stayed aggressive. I really didn't want to walk there. I was just trying to get the barrel on the ball, hit it in the middle of the field."
Manager Jim Riggleman is impressed by the way Desmond doesn't let bad at-bats get the best of him. Before getting the game-winning hit, Desmond struck out twice and hit into a double play.
"Everybody in baseball makes the statement, you have to play nine innings, regardless of what goes on in the ballgame," Riggleman said. "You can't take any of the previous at-bats with you to the plate and take it out on defense. That what Ian does. Every day he goes out there and gives you a good hard nine innings.
"He had a couple of at-bats earlier that he was frustrated with because he didn't think the pitches were strikes. He missed one ball he thought he should have had. He goes out there keeps his head high. Up until that last at-bat, he is totally prepared. Everything else is put behind him and he gives you great at-bats when you need it."
Desmond gave a simple reason as to why he is able to forget about the past.
"I give all my concentration to the at-bat at hand," he said. "I try to give everything I have to every at-bat, try to forget what happened in the past. There is nothing you can do about the past. You are a professional. That's what you are supposed to do."
Relievers Sean Burnett and Drew Storen blanked the Braves the rest of the way, with Storen picking up his fifth save.
"It's a tough loss to swallow," said Braves manager Bobby Cox, whose club is one game from being eliminated from the National League East race. "Nobody on with two outs and we give up three walks and a chopper. They get two runs out of three walks and a chopped ball."
The Nationals took two out of three from the Braves and improved their record to 67-89.
Washington also took the season series, winning 10 out of 18 games from Atlanta. While most of the Nationals feel that beating the Braves is huge boost for next season, Desmond sees it differently.
"We are still going to finish under .500," Desmond said. "We still almost have 100 losses. We still have a lot to work on. Beating the Braves doesn't mean anything. We want to win the division, and we clearly didn't do that."
In the early stages, the Nats built a 2-0 lead against Brandon Beachy after two innings. In the first, Nyjer Morgan scored on a single by Michael Morse. An inning later, Morgan blooped a single to left-center, scoring Ivan Rodriguez.
In his second career start, Beachy had a nice outing, giving up two runs in five innings. He struck out nine and walked three.
However, Nationals right-hander Livan Hernandez couldn't hold the lead. In the fifth, Rick Ankiel led off with a home run over the center-field wall to make it a one-run game.
Two innings later, Melky Cabrera led off with a double to right. Ankiel doubled to right, sending Cabrera home to tie the game at 2.
Hernandez, who threw six-plus innings, was taken out in favor of Burnett, who was able to stop the bleeding by striking out Matt Diaz and Omar Infante and inducing Jason Heyward to ground out to end the inning.
Hernandez reached 200 innings in a season for the first time since the 2007 season when he was with the D-backs. While he is happy to reach the plateau, Hernandez is happy that his team was able to get the victory.
"It's a number I've been looking for and it happened today," Hernandez said. "I'm happy for myself and we won. That is more important."