Not long after the second New York Met trotted around bases in the sixth inning Friday night, a rallying cry circulated throughout Citi Field. During his career, Washington Nationals ace Stephen Strasburg had been praised, anointed and cherished. He had not been openly mocked, not until Matt Harvey gave fans of a beleaguered franchise cause to puff their collective chest. They chanted: “Har-vey’s bet-ter! Har-vey’s bet-ter!”

Both 24, rocket-armed and at the front of their respective National League East rotations, Harvey and Strasburg met for the first of what will likely be many duels Friday night. Round 1 went to the Harvey, a 7-1 Mets victory that featured yet another crucial error from the Nationals’ defense and prolonged the team’s uneven start to 2013.

“It’s funny, because [reporters] want to make a big deal out of all this,” Strasburg said. “But every game is huge for me. I want to go out there. I want to help this team win. It doesn’t matter who’s facing us. We’re out there as a collective group to try to get the job done.”

As Harvey barged into any discussion concerning the very best young pitchers in baseball, Strasburg plodded through six innings. He allowed only five hits and, because of Ian Desmond’s first-inning error, just two of the four runs he yielded were earned. But a high pitch count limited his effectiveness, continuing an April trend. He owns a 2.96 ERA, with 21 strikeouts and seven walks. The same feeling still gnaws at him: He has not yet operated to his high standard.

“Not good enough,” Strasburg said. “It’s tough. I want to go out there and feel great every time. It was kind of a struggle again. It’s still early. I just got to keep battling, keep working hard. I know it’s going to come.”

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 same sentiment applied across the clubhouse. After another lopsided defeat, the Nationals fell to 9-7 overall and 4-6 against opponents other than the Miami Marlins. They have been outscored by 13 runs and have lost by at least six runs four times.

“Any time guys aren’t playing and pitching up to their expectations, players are more disappointed in themselves than anybody,” said third baseman Chad Tracy, who knocked in the Nats’ only run as he replaced Ryan Zimmerman. “I know we keep saying, ‘It’s still early,’ but it’s really early. That’s why we play 162 [games]. The talent will finally show up and the cream will rise to the top.

“We’ve got a lot of improving to do, all the way around.”

With Dwight Gooden watching from behind home plate, Harvey held the Nationals to one run on four hits over seven innings while striking out seven. He fired 98-mph fastballs, unleashed sliders that broke hard and late, twirled tight curveballs and sprinkled in change-ups, just because. For seven innings, Nationals batters took defensive swings against Harvey, as if they couldn’t guess what pitch was coming next and weren’t sure if they could hit it even if they did. He let the Nationals know what other teams felt when they unleashed Strasburg on the league.

“He’s got good stuff,” Desmond said. “Simple as that.”

Desmond’s error allowed the first hitter of the game to reach base, a fitting start to Strasburg’s arduous night. The Mets used the miscue, two singles and a run-scoring wild pitch to take an instant 2-0 lead.

Strasburg allowed the leadoff batter to reach in five of his six innings, but he still did not yield an earned run until the sixth. Ike Davis pummeled the first pitch of the inning, Strasburg’s 97th overall, deep over the left-center field fence for an opposite-field homer. Five pitches later, Lucas Duda banged another solo homer, giving Harvey and the Mets a 4-0 lead.

“I’m not having good enough feel early to just go out there and let it eat and get through some quick innings to get deep in the ballgame,” Strasburg said. “That seems to be the case the last few starts. Going out there, just not throwing enough strikes early. It’s kind of shooting myself in the foot.”

The Nationals had one more chance to leap back into the game, one more chance to chip away at Harvey. The Nationals loaded the bases with no outs in the seventh against Harvey, scoring a run on Tracy’s RBI single in the process.

Harvey had allowed only two hits before the seventh, and Strasburg himself supplied the Nationals’ lone extra-base hit, a double to the right field corner in the third. Harvey’s most impressive work, though, came in squelching the Nationals’ last-gasp rally. Kurt Suzuki whiffed on a 3-2 fastball.

Manager Davey Johnson said he was “tempted” to pinch-hit with Zimmerman, but chose caution with Zimmerman’s tight hamstring. Instead, pinch hitter Roger Bernadina popped foul to the catcher. Denard Span rolled a groundout to second base. The bases emptied, and Harvey stomped off the mound with a roar.

“It looked like his velocity was starting to go down a little bit,” Tracy said. “I think he dialed it back up again when he had the bases loaded. That was our opportunity, and we didn’t really take advantage of it.”

The Nationals had squandered their best chance, but their loss had started from the outset. In the first inning, leadoff hitter Jordany Valdespin rolled a slow grounder toward shortstop. With Valdespin’s speed, Desmond needed to charge and make a quick, accurate throw. In his rush, the ball deflected off his glove. Valdespin cruised through first base and the ball dribbled around the mound.

“Booted it,” Desmond said. “I make it more times than not, but what are you going to do?”

For all the consternation over Zimmerman’s throwing mechanics, Desmond has committed six errors this season to Zimmerman’s four. Desmond has cut his error total from 34 as a rookie in 2010 to 23 in 2011 to 15 last season. No major leaguer has made more than him in 2013. With 10 coming from the left side of their infield alone, the Nationals have committed an MLB-high 15 errors. Recently, almost all of them have led directly to damage.

“I like our defense,” Johnson said. “We just haven’t made the plays, and we haven’t pitched well behind errors.”

Any hope the Nationals had Friday night evaporated in the eighth inning, during a horrific inning for Drew Storen. David Wright drilled a triple, Davis crushed an upper deck home run to right field and Duda smacked his second homer before Storen could record his second out.

Harvey overwhelmed from the first pitch, a 96-mph fastball Span took for a strike. After Harvey threw a curve for strike two, he blazed a 98-mph heater past Span. When Desmond led off the second, Harvey blew him away with a fastball at the shoulder.

“He pitches in there with a purpose,” Tracy said. “He’s trying to make it look good to us, but his ball kind of takes off at the end, up. By the time you think you’re on it, it’s gone.”