Jonathon Niese, above, outdueled Nationals starter Edwin Jackson on Saturday night. (Patrick McDermott/GETTY IMAGES)

The season is arduously long and these nights will happen. The Washington Nationals will stumble when an opposing pitcher catches lightning and suffocates their scalding offense. Their pitchers will dominate for large swaths of the game only to make a few mistakes that change the game. So far this season, such slip-ups have occurred less often than not.

Edwin Jackson plowed through the New York Mets’ lineup Saturday night with a cutting fastball and devastating slider, striking out a season-high 11 batters, only to falter by allowing a two-run home run in the seventh. The Nationals’ offense, baseball’s highest-scoring in the second half of the season, could muster only five hits and push one hitter past second base. And as a result, Washington fell to the Mets, 2-0, before a packed house at Nationals Park.

“Those games will happen every now and then,” third baseman Ryan Zimmerman said.

But there’s no mistaking the Nationals’ position: They still carry baseball’s best record. They maintained a four-game lead in the National League East, as the Atlanta Braves lost at home to the Los Angeles Dodgers. The Nationals could reflect on a wasted opportunity but move on to the next challenge just as quickly.

Even though they fell on Saturday, they stand 28 games over .500, an achievement last accomplished by a Washington baseball team in 1933. They could nab the series from the Mets on Sunday, and move on to face the Braves on Monday. It’s mid-August, and there’s much more to come.

“Every night you get a chance to add [to the division lead] . . . or to lose ground,” first baseman Adam LaRoche said. “We’re not going to win out the rest of the games. This’ll happen again. It’s part of it.”

Also part of a pennant race is a re-energized fan base that can fill Nationals Park with 42,662 people on a late-summer night as it did Saturday — the second-largest crowd in the stadium’s four-year history. They were treated to a pitchers’ duel.

Every Nationals starter has a distinguishing pitch in his superb arsenal. Gio Gonzalez has a freezing curveball and Jordan Zimmermann has a biting slider, to name a few. Jackson has a dipping, disappearing slider.

On Saturday, that slider, which sat between 84 and 86 mph, was a dangerous complement to his tailing and sinking fastball, which ran between 92 and 94 mph. “I was able to come out and throw that a lot,” Jackson said.

Take this sixth inning at-bat against Mets leadoff hitter Ruben Tejada: On the first pitch Jackson threw an 85-mph slider, which Tejada let fly by, sizing it up. Jackson offered another slider: a swing and a miss. Tejada then fouled off two 93-mph fastballs and faced an 0-2 count. Jackson unfurled another slider. It started near the lower half of the plate and when Tejada swung at it, the ball vanished, dropping straight down like a free-falling anvil.

The most telling post-strikeout reaction of the night belonged to Mets first baseman Ike Davis, who, after striking out in the fourth inning on a slider, stared back in disbelief as he trudged off to his dugout uttering a not-so-cheery word to himself.

“That was probably the most dominant I’ve seen him pitch,” Nationals Manager Davey Johnson said of Jackson.

Other than a leadoff triple in the first inning, Jackson’s only mistakes occurred in the span of two batters in the seventh inning. His command wavered against David Wright, who drew Jackson’s only walk of the night. The last pitch of the at-bat misfired badly, sailing high and dropping Wright onto his backside.

Jackson then released a fastball over the middle of the plate to Davis, who hammered the ball the opposite way to left field, a two-run blast. Jackson didn’t show much emotion until he finished the inning with his 11th strikeout of the night. He ambled toward the dugout with his mouth pressed into his glove, shouting at himself.

Jackson “probably threw less bad pitches” than Mets starter Jonathon Niese, LaRoche said. “I mean, hittable pitches. And one of them happened to leave the park. It’s tough.”

The Nationals’ offense could do little to boost Jackson, even when it escaped Niese in the eighth inning and faced the Mets’ bullpen, statistically the worst in the majors.

The Nationals mounted their best offensive threat in the first inning. Danny Espinosa smacked a single to left field with one out, and Zimmerman followed with an opposite-field single.

Michael Morse’s deep flyout to right field moved Espinosa to third and Zimmerman stole second in the next at-bat. But LaRoche grounded out to end the inning. Third base was the furthest any Nationals hitter would reach in the game.

Facing the Nationals for the second time this season, Niese fooled his opponents with his command, a cutting fastball and a dancing, change-of-pace curveball. He neutralized a leadoff single by Espinosa in the sixth inning by inducing a flyout from Zimmerman, striking out Morse with another cutter and forcing a groundout by LaRoche.

The Nationals fell in order in the ninth, though Zimmerman roused fans to their feet when he drilled a ball deep to right field to lead off the inning. Right fielder Mike Baxter tracked down the slicing ball, catching it and slamming into the wall. The Nationals’ best chance at sparking a rally rested in the fielder’s glove.

“I really don’t know why he was there,” Zimmerman said. “But he got me out so it worked.”

Two outs later, the Nationals would retreat to a silent clubhouse, a feeling they haven’t experienced as often this season, but one that they could remedy in a few hours.

“Didn’t work out,” LaRoche said. “Get ’em tomorrow.”