Denard Span and the Nationals head to Atlanta for a key NL East showdown this weekend. (Photo by Toni L. Sandys/The Washington Post) (Toni L. Sandys/The Washington Post)

For much of the past two months, the Washington Nationals have hovered in or around first place in the National League East with little wiggle room between them and the Atlanta Braves. But the past week has pushed both teams in different directions. Ahead of the biggest series between the two this season, the Braves are in a free fall and the Nationals arrive in Atlanta with their biggest division lead — 41 / 2 games — of the season .

“They just came off an eight-game losing streak, so they’re going to want our throat,” Nationals left fielder Bryce Harper said after Thursday’s walk-off win.

Beginning with this weekend’s three-game showdown in Atlanta, the Nationals will face the Braves nine times over the final seven weeks of the season. The Nationals can potentially dig a deeper hole for their rivals — or breathe new life into the Braves’ season.

The best-case scenario for the Nationals — sweeping the Braves — would give them a 71 / 2-game lead with 46 games to play. If the opposite were to happen, the Nationals’ lead would be slashed to 11 / 2 games.

“They’ve been the biggest hurdle for us since I’ve been here,” center fielder Denard Span said. “If we’re going to win this division, we’re going to have to find a way to beat them. They’re the reigning division champion. If we want to be NL East champions, we’re going to have to go through them and beat them and prove to them that we deserve this.”

The Post Sports Live crew talks about whether the Nationals’ trade for infielder Asdrubal Cabrera significantly improves the team or adds just another league-average bat. (Post Sports Live/The Washington Post)

The Braves are one of the main reasons the Nationals finished four games out of the playoff last season. The Nationals played the Braves well in 2012 en route to their first division title. But since the start of the 2013 season, the Nationals are 9-20 against Atlanta; they are 3-7 this season.

“I tell you what, [41 / 2] games feels like a lot of games to be ahead compared to last year and fighting from behind all last year,” reliever Craig Stammen said. “And even this year, it felt like we were a little bit behind or barely ahead. I think just like last year, all our series against the Braves, the 18 total games, are going to determine who wins the East. We have to prove that we can beat them and prove that we are the National League East’s best team.”

The Braves’ struggles began after the all-star break. Since then, they are 6-13, capped by a winless three-city West Coast road trip in which they were swept by the Dodgers, Padres and Mariners. For the first time in more than two years, the Braves have lost eight in a row. Their already inconsistent offense scored only 18 runs in those eight games against tough opposing pitchers, and their normally stout pitching allowed 41 runs. Their pitching staff has a collective 3.40 ERA, seventh best in baseball, and has buoyed the offense, whose .678 OPS ranks 26th in baseball.

“We are not too far out of it and we have a chance to get back into it this weekend,” Braves first baseman Freddie Freeman told Atlanta reporters following Wednesday’s loss.

Because of the strength of the Atlanta’s bullpen last season, the Nationals were 3-5 against the Braves in one-run games. The Braves’ bullpen led the majors with a 2.46 ERA last season. But this season, injuries have made it less dominant; its 3.28 ERA is 10th best in the major leagues.

“We’ve played a lot of close games,” Stammen said. “I can’t remember them blowing us out very often or us blowing them out very often. I feel like every game has come down to the seventh, eighth inning. They seem to be getting a few of the breaks. I think the last two games we played here, we got it and go ahead of them and beat them. They’re big for us and our psyche.”

The last time the Braves and Nationals played, the Braves took the first two games of a four-game series in Washington, but that Nationals split the series thanks to strong pitching performances by Doug Fister and Tanner Roark. Stephen Strasburg, Gio Gonzalez and Roark are scheduled to face Atlanta this weekend.

Turner Field has been, in a way, a house of horrors for the Nationals. Since 2013, the Nationals are 4-9 in Atlanta, including three walk-off losses. In that span, the Nationals have suffered injuries to Harper (side), Span (concussion), Strasburg (oblique) and Ryan Zimmerman (thumb).

“There’s always something crazy going on,” Span said. “It’s never a normal clean game. If we have a pretty big lead, they find a way to make it interesting. We’ve played extra-inning games there. We’ve done it all there. It’d be nice to go in there and win the series and just play good, clean baseball.”

At this point of the season, scoreboard watching is only natural. Few Nationals may admit it but they’re keenly aware of the Braves and where they stand.

“I’ve always said we need to take of ourselves and whatever happens with other teams happens,” first baseman Adam LaRoche said. “So regardless, they’re still a very dangerous team. We need to go into Atlanta knowing that. Especially against us this year, they’ve been really, really good. They bring their ‘A’ game. I don’t know. They’re a good ballclub. It’s a matter of time before they turn it around. That’s why we need to keep doing our thing and not worry about that.”