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 feeling, missed but not forgotten, told Bryce Harper everything. The barrel of his bat carved through the strike zone, arms extended at the moment of contact. It had been a long season for him. It had been a long Thursday for the Washington Nationals. “I knew it was gone,” Harper said. “I felt it.”

Mired in a slump, the focus of constant scrutiny, Harper blasted a two-run, walk-off home run in the 13th inning that represented both the decisive blow in the Nationals’ 5-3 victory over the New York Mets and a burden lifted. Harper smashed the afternoon’s 374th pitch four rows deep to the left of the visitors’ bullpen — an “oppo-boppo,” in Harper’s parlance.

Teammates spilled from the home dugout. Harper floated to first base. He raised his bat in the air and dropped it like a used toothpick. He raised his right fist as he rounded first and pumped it as he trotted to second.

“I haven’t felt like that in a while,” Harper said.

Harper’s first home run since July 18 pushed the Nationals’ lead in the National League East to 41 / 2 games as they packed for Atlanta for a three-game weekend series with the reeling Braves.

The Post Sports Live crew debates what the odds are that the division-leading Baltimore Orioles and Washington Nationals meet in the World Series. (Post Sports Live/The Washington Post)

So much had to happen for Harper to have a chance. The Nationals needed six scoreless innings from their bullpen, the final three from Craig Stammen. They needed Ian Desmond’s own slump-breaking homer, a two-run shot in the second inning.

But it ended with Harper standing in front of his dugout, doused with a bucket of orange liquid and another jug of water.

“Gatorade is going to be pretty happy about that,” Harper said, laughing.

One day earlier, Harper’s slump had given rise to the existence of a debate, however silly, of whether Harper should take the search for his swing to the minor leagues. In 31 games since he returned from the disabled list, Harper had hit .218 with five extra-base hits and 36 strikeouts in 118 plate appearances. He cycled through batting stances, sometimes within the same game. He searched for his swing. On Thursday, when the Nationals needed it most, he found it.

“He needed that probably more than any hitter in the big leagues,” Stammen said. “We were all excited just for him, so we see a smile on his face tomorrow at the ballpark. Because it’s hard. This game eats you up.”

The Nationals had surged into first place as their most dynamic player struggled in his return from thumb surgery. “Everybody’s been picking up my slack, pretty much,” Harper said. As the Nationals packed for Atlanta, they already began thinking about how Harper’s game-ending swing may carry over and what it could mean.

“It’s huge, man,” said Denard Span, who continued to stay hot by going 4 for 6 to raise his average to .300 and extend his on-base streak to 33 games. “We need to get him going. When he’s hitting, it makes us 10 times more dangerous. It makes the lineup obviously deeper. Hopefully he takes that and builds off of it and keeps it going this road trip.”

“In my mind, I’m hoping so,” Harper said. “But of course, you know this game. You go into every single day, and it’s nice to be able to start over every single day. You go 0 for 4 one day, 4 for 4 the next day. That’s just part of the game. Hopefully we keep winning ballgames and stay in first place. We’ve got a great team.”

The Nationals took a 3-1 lead into the seventh before Jordan Zimmermann ran into trouble and left with two runners on. Drew Storen allowed both to score, and the teams engaged in a stalemate through extra innings. The Nationals marooned base runners. The Mets flailed against Tyler Clippard, Rafael Soriano, new addition Matt Thornton and Stammen.

“Very valuable to have a guy like him that can go that many pitches and run you through some innings and keep them where they’re at,” Manager Matt Williams said.

As Stammen chewed up outs, the Mets ran through their entire bullpen. Carlos Torres, the last reliever standing, entered in the 13th. Desmond welcomed him with a walk. Harper walked to the plate.

Harper had stung both a single and a lineout and was 1 for 5 when he stepped in against Torres. He believed the solid contact he made Thursday afternoon was indicative of his recent stretch.

“I don’t think I’m struggling where it’s to the point where anything looks terrible,” Harper said. “Of course I’ve been struggling a little bit. I’ve hit some balls that have just been right at people sometimes. You just got to tip your cap and play this game. The game is pretty humbling sometimes. I just try to have fun and come in here and laugh and smile.”

Late in Wednesday night’s 7-1 Nationals victory, Torres struck out Harper with a curveball down and in. Harper did not think Torres would throw him any pitches over the plate. “Hit a ball to left center,” Harper told himself. “Try to win a ballgame.”

Torres started Harper with his best pitch, a cutter, and Harper took it as it veered toward his belt buckle. Torres surprised Harper with the location of his next pitch — thigh high, over the outer third of the plate.

“I’ve got to look [on the replay] and see what it was,” Harper said. “I was just trying to barrel something. I was just trying to get something out over and try to punish it.”

It was a 91-mph fastball, and Harper walloped it. He knew right away. As Harper rounded third, he pointed into the stands. He chucked his helmet just before he arrived at home plate and disappeared into a sea of teammates.

“Something like that, that’s big,” Desmond said. “Hopefully he rides that for the next couple months and we sail off into the sunset.”

Harper escaped from the pack between the mound and third base. Span grabbed him, gave him a high-five and hugged him. Jayson Werth wrapped his arms around him. Teammates formed a line to embrace him. Harper slicked his hair back and smiled. What must that have felt like?

“When everybody is pulling on the same rope, it’s fun to play,” Harper said. “It’s going to be a lot of fun this next month and a half.”