Ryan Zimmerman doubles in the first inning against the Braves. (Dave Tulis/Associated Press)

A week ago, Ryan Zimmerman’s outlook was bleak. His offensive numbers were in a tailspin, as the previously consistent hitter whiffed miserably at pitches he normally smacked for hits. With nagging pain in his right shoulder, a trip to the disabled list for the second time this season seemed likely.

But Zimmerman found his magic potion: a cortisone shot in that ailing shoulder eight days ago that alleviated his discomfort and helped him relax. Since then, it has been a near night-and-day difference for the Washington Nationals’ cornerstone third baseman. His offensive onslaught continued on Sunday, his best day at the plate this season, driving in a season-high four runs in an 8-4 win over the Atlanta Braves on another scorching afternoon.

“He just looks happier,” Nationals Manager Davey Johnson said.

Zimmerman’s emergence has come at the most opportune of times for the Nationals. Before last week — and before a therapeutic trip to the thin air of Colorado, where offenses come alive — the Nationals’ offense was sputtering at 3.73 runs per game, the fourth-lowest mark in the major leagues.

Now that Zimmerman, the team’s third-place hitter, has come alive along with the heart of the team’s batting order, the Nationals have slowly climbed from the offensive cellar. Entering Sunday’s game, they had improved to 4.05 runs per game in only seven days. Zimmerman has been a vital complement to the also-emerging bat of cleanup hitter Michael Morse and the consistent production of fifth-place hitter Adam LaRoche.

“We’re getting healthier,” Zimmerman said. “We’re getting more consistent. The more you can throw out the same lineup, the more consistent you’re going to be. For the first half of the year, we’ve kind of had to shuffle things around. It’s not easy to score runs when different guys are in different places and you don’t really get to settle into the role.”

Added Johnson: “With him and Michael Morse swinging the bat, we can have some fun in the second half. No doubt about it.”

Over the first 55 games of the season, Zimmerman hit .218 with three home runs. In the eight games since, he is hitting .389 (14 for 36) with three home runs and 10 RBI.

Maybe the high altitudes and thin air aided his four-game tear in Colorado last week, but the home run he launched in the fifth inning of Sunday’s game was no fluke. Facing a 1-1 count, Braves starter Tim Hudson tossed Zimmerman a slow curveball. Entering the game, Zimmerman was hitting a measly .200 in 50 at-bats against the Braves’ right-hander.

Zimmerman turned on the pitch and smashed it into the second section of seats in the lower tier of Turner Field, more than 15 rows back of the left field fence. His solo shot, his sixth of the season, gave the Nationals a 6-1 lead.

Washington pounced on Hudson in the first inning, grabbing a quick 4-0 lead thanks, in part, to Zimmerman. In his first at-bat of the game, Zimmerman drilled a low pitch deep into center field and off the base of the wall for a two-run double. After a run-scoring single in the ninth gave him three hits on the day, Zimmerman is now hitting .241.

Nationals starter Gio Gonzalez, who was told he was named a National League all-star only hours before the game, turned in a hard-fought outing in unbearable heat, allowing four runs on five hits over five-plus innings.

Battling the heat that registered 101 degrees on the thermometer but felt like much more, Gonzalez was chased in the sixth inning after two walks and a three-run homer by Freddie Freeman cut the Nats’ lead to 6-4. He was wearing down in weather similar to that of Saturday’s game, when Nationals starter Stephen Strasburg left the game with dehydration. Gonzalez was already at 98 pitches to start the inning.

“You just have to go out there and try to overcome it,” said Gonzalez, who improved to 11-3. “Every inning I was in there taking off my shirt, putting on some cold towels, just trying to stay cool and lower the temperature on my body.”

Before this series win over the Braves, the Nationals were in first-place in the National League East in spite of their offense and thanks to their pitching. On Sunday, thanks to both, they won and claimed their sixth win in eight chances over the division rivals.

“Nine hits a ballgame, that should be our low with the talent on this ballclub,” Johnson said.