Atlanta pulled within 2½ games of Colorado for the NL wild card when the Rockies lost 6-3 to St. Louis, which clinched the NL Central title.The Braves (84-70) have won 13 of 15 and are 50-30 since June 27, improving to a season-best 14 games over .500.
Hanson (11-4) allowed four hits and four runs -- three of them on Mike Morse's pinch-hit homer. The right-hander, who made his major league debut on June 7, struck out seven and walked one.
"Since I've been up here, we've been playing really well," Hanson said. "Hopefully, we keep winning games and get lucky."
"It's getting to be a lot more fun," manager Bobby Cox said. "I think we're pretty good right now."
It's going to be difficult for Atlanta to catch the Rockies, but the Braves have four more games against the woeful Nationals, who lost for the 102nd time, matching their total from last year with eight games remaining.
Catcher Brian McCann said the 6-foot-6, 23-year-old Hanson has played a key role in launching the team into contention.
"What he brings to the team is a guy who has No. 1-type stuff," he said.
The Braves took advantage of Washington's shoddy defense to jump out to a 5-0 lead. Yunel Escobar had a two-out, two-run single off Garrett Mock (3-10) in the first and third baseman Pete Orr's throwing error on Matt Diaz's slow roller led to two more runs.
Orr got the start in place of Ryan Zimmerman, who pinch hit in the eighth inning and flied out.
Right fielder Elijah Dukes committed the first of his two errors in the second, muffing Chipper Jones' fly ball for a two-base miscue that allowed Martin Prado to score. Dukes also committed an error in the ninth.
Washington has allowed five unearned runs on four errors in the last two games.
"If it could go wrong, it went wrong," Nationals manager Jim Riggleman said. "Freakish things are happening."
Atlanta broke it open with five runs in the ninth. McCann hit a two-run homer, Jones and Escobar had RBI doubles and LaRoche singled in a run.
"You can't really take any hitters off in our lineup," Jones said. "It was just a matter of time before we put it all together and started rattling off wins."
Mock, who lost his fifth consecutive decision, allowed six runs, four earned, and seven hits in five innings. Willie Harris had a two-out RBI single in the third, Morse connected in the fifth and Ian Desmond added a sacrifice fly in the ninth for Washington.
- Riggleman said Zimmerman is a little banged up. "He's been playing through some nagging stuff," Riggleman said. "He's sore in a couple of different areas." Zimmerman expects to play Sunday. "I think everyone is banged up right now," he said.
- Nationals SS Cristian Guzman may not play in the field again this season. He's suffering from a sore shoulder, which has limited him to pinch hitting.
- Washington LHP Sean Burnett, whose bruised left thumb has hampered him, may not pitch again this season. "I doubt if we'll use him. That bone contusion has not gotten better," Riggleman said.
- Atlanta is 45-35 on the road and 39-35 at Turner Field.