Despite surrendering a pair of leads Saturday at Citi Field, the Nationals escape as their bullpen allows just one run in five innings after starter Gio Gonzalez was lit up in the fifth inning. (Al Bello/Getty Images)

Concerns have mounted for the Washington Nationals earlier and with more frequency than expected, and the best solution to each so far has been the same. When something goes wrong, when the bullpen loses another lead or another ace implodes, wait for Bryce Harper and watch what he does next.

By the eighth inning Saturday afternoon, Gio Gonzalez sat in the dugout wondering what had gone wrong. Ryan Zimmerman digested his coming stint on the disabled list. The New York Mets had erased two deficits. To the plate walked Harper, part wrecking ball, part balm for whatever ails his team.

Harper obliterated the first pitch Josh Edgin threw him over the bullpens in right-center field, lifting the Nationals to a 7-6 victory Saturday afternoon at Citi Field and capping his own memorable performance. Harper demolished a two-run homer to give the Nationals breathing room, belted a double in a crucial rally that gave them the lead back and, lastly, smashed the game-winning solo homer in the eighth inning.

“Harper,” Manager Davey Johnson said, “was amazing.”

The Nationals have subjected themselves to a surprising abundance of gloom. Their bullpen has leaked oil, their defense has mangled games and their starting rotation has resembled a sine wave. But they have still won 10 games against seven losses. The primary reason is Harper. Through 17 games, the 20-year-old Harper has slugged .758 with a .426 on-base percentage and 14 RBI. All seven of his home runs have come either with the score tied or in a one-run game.

“Whenever he hits a home run, it seems like it’s in a very important situation,” reliever Craig Stammen said. “He doesn’t ever hit them when we’re down 10 or up 10. He always hits them when it’s a close game. That’s how special of a kid he is. It’s awesome.”

Saturday, Harper had help in offsetting Gonzalez’s five-run debacle in the fourth inning. After Harper’s two-out double in the fifth, first baseman Adam LaRoche crushed a three-run homer that turned a 5-3 Mets lead to a 6-5 edge for the Nationals. Led by Stammen’s two powerhouse innings, Tyler Clippard’s 11 / 3 scoreless frames and Rafael Soriano’s sixth save, the Nationals’ bullpen redeemed some early failings.

“Davey always preaches the 25th is just as important as the first guy,” Stammen said. “That’s how we won so many games last year. That’s how this team is going to win a lot of games this year, too.”

Sunday, there will be a 26th guy. The Nationals called up top prospect Anthony Rendon to replace Zimmerman, whom the team expects to miss no more than the mandatory 15 days with a strained hamstring. Rendon will likely bat sixth at Citi Field in his debut.

Thanks largely to Harper, he’ll try to help win the series. With the score tied at 6, Harper led off the eighth inning against Edgin, a burly left-hander. He pairs a mid-90s fastball with a “pretty good hook,” Harper said. He wanted to hit a fastball before Edgin could mix in his curveball. He didn’t necessarily want to swing at the first pitch, but he definitely looked for the first good pitch to hit.

“You got to get him early,” Harper said. “Because when you try to get him late, you’re really in trouble.”

Edgin fired a 93-mph fastball, and Harper vaporized it. The ball rocketed over the bullpen and clanged off a Dunkin’ Donuts billboard. Stammen had only seen one other ball travel so far at Citi Field. “That’s Adam Dunn territory,” he said.

The Post Sports Live crew discusses whether the Nationals bullpen woes, Ryan Zimmerman’s throwing errors and Wilson Ramos’s injury are reasons to worry. (Post Sports Live)

The Nationals led 7-6, and finally the seesawing stopped. They had taken an early 3-0 lead on home runs from Ian Desmond and Harper off starter Jeremy Hefner. Gonzalez cruised into the fourth, then allowed a leadoff triple to David Wright and walked John Buck. Gonzalez nearly worked out of the jam when he induced a weak comebacker from Ike Davis and got Marlon Byrd to ground to Chad Tracy, who ensnared Wright in a rundown for the second out.

“You get one good pitch, down-and-away, get out of the inning with no damage,” Gonzalez said.

Instead, Gonzalez endured a meltdown. The next five batters reached on three singles and two walks. The Mets pulled ahead, 5-3, and Gonzalez, after throwing 41 pitches to escape the inning, would not throw another pitch. Without warning, Gonzalez had gone from pitching a gem to hitting the showers.

“There’s things you can’t explain,” Gonzalez said. “I was sitting there contemplating what happened. You’re dominating, and then all of a sudden. . . . ”

Another lead had disappeared, another ace had been dispatched and another slice of promise threatened to slip away. It is hard to need anything in April, but the Nationals needed a spark, a glimmer — something.

Jayson Werth drew a walk. That was something. Against left-hander Aaron Laffey, Harper fell behind in the count, taking a weak cut way in front of Laffey’s 85-mph fastball. He made an adjustment, took a ball, fouled off a strike and then smashed an opposite-field double to the left field corner.

The inning fell to LaRoche. He fell behind, 1-2, when he swung and missed at a fastball. Laffey tried to finish him off with another, but he left it over the plate’s heart. LaRoche uncorked his elegant swing and clobbered the pitch. The ball flew over the left-center field fence, and the Nats led, 6-5. When Harper crossed the plate, Werth greeted him with an emphatic double high-five.

“It just seemed like every one was playing their part,” Gonzalez said. “They see their starter going through a rough patch, they’re going to help him and they’re going to try to pick him up. That’s what a team is all about.”

The Nationals led, but their bullpen — which entered with an MLB-worst 5.70 ERA — needed to protect a one-run lead, possibly for five innings. Over two innings, Stammen faced six batters. He retired them all, struck out five and induced eight swing-and-misses in a span of 35 pitches. His two-seam fastball darted like a balloon running out of air. He put the Mets’ bats in a vise.

Once he left, the Nationals still had three more innings to hold on. They couldn’t keep the lead for one. In the seventh inning, Ryan Mattheus allowed a run on an infield single and John Buck’s double, but that was all the Mets could muster against four relievers.

“We haven’t really been getting it done so far this year,” Clippard said. “That’s a big part of why we’re going to be successful in the future. It was good to get in there and shut the door like we did.”

Harper, of course, was the one who opened it. The Nationals may have their problems through the first three weeks. But they also have Harper, and that may matter more than anything.