WASHINGTON — It’s back to the heavyweight portion of the schedule for the Mets.

If there is any doubt they can handle it — a five-game series against the Braves over four days beginning Thursday at Citi Field — the Mets only have to reflect on their successful trip to Atlanta the week before the All-Star break, in which they won two of three contests against a team that had been closing in the standings.

Since then the race has largely stabilized. The Mets, with their 9-5 victory over the Nationals on Wednesday, extended their NL East lead on the Braves to 3 ½ games. The Mets, who won five of six games on the road trip, have picked up a game on the Braves since the finale of their series in Atlanta on July 13. The Mets’ lead over the Braves on May 30 was 10 ½ games.

“When you look at the schedule and everything, you hope you’re in it,” Braves manager Brian Snitker told Atlanta reporters. “Shoot, after you play 100-and-whatever games, this is where you want to be. You want to be in this position, where these games are big.”

The next five games won’t decide anything, but the Mets still have two trips to Atlanta remaining (including one within the final week of the season) that combined with these five could carry significant weight in determining who wins the division and who is reduced to playing in the wild-card round. The two division winners in each league with the best records will receive a bye in that first round.

The Braves added bullpen, rotation and lineup fortifications at the trade deadline: Raisel Iglesias, Jake Odorizzi, Robbie Grossman and Ehire Adrianna. The Mets were active, but more conservative, with their acquisitions of Daniel Vogelbach, Tyler Naquin, Darin Ruf and Mychal Givens.

“They are a real good team and they are playing good baseball,” Vogelbach said. “But we’re a real good team and we’re playing good baseball.”

On this day, the Mets received a loud hit from Vogelbach and strong pitching performance from Chris Bassitt in handling the gutted Nationals in their second game since they traded Juan Soto and Josh Bell to San Diego.

Vogelbach’s first homer in a Mets uniform — a grand slam in the fifth — broke the game open, burying the Nationals in a 6-0 hole. The lefty-hitting Vogelbach entered the day with a .483 on-base percentage in eight games since arriving in a trade with Pittsburgh for reliever Colin Holderman.

Brandon Nimmo walked to begin the inning against Anibal Sanchez before third baseman Ildemaro Vargas dropped Starling Marte’s line drive and threw the ball away, placing runners on second and third. Pete Alonso was intentionally walked and Vogelbach greeted reliever Jordan Weems by smacking a 97-mph fastball over the right-field fence.

“It’s easy to feel comfortable when you come to a team like this,” Vogelbach said. “Not just the players on the field, but the players off the field. It’s an easy clubhouse to come into — there’s a lot of really good people in this clubhouse and it makes you feel welcome and it’s easy to feel comfortable.”

Alonso’s two-run homer in the third gave the Mets a 2-0 lead. The blast was his second in the series and increased his total to 28 for the season, which ranks fifth in MLB. Alonso’s 88 RBIs are second to Aaron Judge’s 93. Francisco Lindor’s two-out walk in the inning started the rally after Marte had grounded into a double play.

Bassitt pitched seven shutout innings, allowing six hits and one walk. It was the right-hander’s fourth performance this season in which he pitched at least six scoreless innings.

In his Mets debut, Givens allowed five runs in the ninth inning, forcing manager Buck Showalter to summon Seth Lugo to record the final out.

“[The Braves] beat us to New York,” Showalter said. “But they are a real good team and we have our work cut out for us.”