Lannan controlled the Mets’ potent lineup, allowing just one hit and one run while striking out seven batters in seven innings. The Nats (57-93) led 2-1 entering the sixth. But Anderson Hernandez had a two-run single in that inning and Elijah Dukes followed with a three-run home run in the seventh.

“The last three [starts] I felt good, but still struggled a little bit. So I didn’t know what to think coming into this game,” Lannan said. “But I didn’t try and change anything. I just went out there and threw the game I knew I could.”

Last week, Lannan gave up five runs on eight hits, including two monster homers by left-handed batters Ryan Church and Carlos Delgado in that three-inning effort. It continued a worrying trend for the 23-year-old. Since pitching six innings with no runs allowed in a game at Milwaukee on Aug. 10, Lannan had been shaky in three of his next five starts.

There was the eight-run outing against Colorado and a pair of five-run games against the Mets and Chicago Cubs. Granted, in between were solid starts (two runs, six innings) against both Philadelphia and the Los Angeles Dodgers. But at 163 innings pitched entering the night, Lannan had already set a career high in that category. He denied fatigue was a factor, however.

“I think it says a lot about the kid taking into consideration such a rough start he had last time in New York,” Nats manger Manny Acta said. “And then coming over here today and pitching the way he pitched — that’s why we like this kid so much.”

Lannan’s change-up baffled New York hitters all evening, especially Delgado and Church. He struck out Delgado and No. 3 batter David Wright swinging twice each. Church was 0-for-2 with a strikeout and a walk. The Mets’ top five batters were a combined 0-for-13 with five strikeouts and just two walks against Lannan and for the night, Jose Reyes, Church, Wright, Carlos Beltran and Delgado were 2-for-18.

It was a talk with Nats left-hander Odalis Perez in recent days that gave Lannan the idea to throw his change-up to left-handed batters — something he had avoided prior to last night.

“And it’s a great concept. I was just never was really comfortable doing it,” said Lannan, now 9-13 with a 3.97 ERA. “And then tonight I was just like … I’m going to try it. It’s something to work on, another kind of weapon.”

The Nats opened the scoring in the first inning when Willie Harris scored on a 4-6-3 double-play grounder by Ryan Zimmerman. They added another run in the fourth when Lastings Milledge doubled and Aaron Boone singled him home two batters later.

The Mets played their own version of small ball to produce a run in the third. A leadoff double by former Nats catcher Brian Schneider, a sacrifice by starting pitcher Pedro Martinez and a fielder’s choice grounder by Reyes tied the game at 1.

But the Nats extended their lead to 4-1 against Martinez (5-5, 5.47 ERA) in the sixth. Zimmerman singled — his first career hit against Martinez — and, after an out, Elijah Dukes walked. They moved up a base when Boone hit a dribbler in front of the mound. Then Hernandez came through, ripping a clutch single past a diving Delgado and into right to score both runners.

Things fell apart for the Mets in the seventh. With two outs and no one on base, manager Jerry Manuel went to right-handed reliever Duaner Sanchez. Zimmerman promptly walked and Milledge singled. That brought Dukes to the plate and he smashed a breaking ball over the fence in left for his 12th homer of the year and sixth in the last 17 games. That made it 7-1 and effectively put the game out of reach.

The Mets briefly threatened in the eighth. Reyes singled home Luis Castillo to make it 7-2 and Church followed with a hard base hit off Nats lefty Mike Hinckley. But Acta allowed Hinckley to remain in the game to face the right-handed Wright, who came to the plate with two on base and one out. What was supposed to be a down-and-away fastball on a 2-0 pitch instead missed up and in. No matter. Wright chopped the ball towards shortstop for a 6-4-3 double play.

“That’s a good spot to miss,” said Hinckley, who has not been scored upon in 8 1/3 innings since making his major-league debut Sept. 2 and has given up just four hits and a walk during that stretch. “If I would have missed out over the middle of the plate it probably would have had a different story.”

Nats notes


» Nationals manager Manny Acta said catcher Jesus Flores is not close to returning from the severe ankle sprain he suffered against Philadelphia on Sept. 2.

“He was checked again by the doctor and right now things aren’t looking very good because he’s still feeling some pain when he squats,” said Acta, who noted Flores would undergo another MRI to make sure the injury is healing properly. “He might be done [for the season].”

» The Mets (83-66) have now lost three of their last four games and seen their lead in the National League East sink to ½ game over second-place Philadelphia. The Phillies (83-67) were idle Monday night and begin a three-game series at Atlanta tonight.