NEW YORK -- The New York Mets pulled out all the stops -- starting position players promoted Friday from Triple-A and employing starting pitchers as pinch-hitters and pinch-runners -- to try and win Friday night.

None of it was enough, because the Washington Nationals have Bryce Harper.

Harper hit a two-run homer in the first inning and scored the go-ahead run in the 11th as the Nationals beat the Mets 4-3 in the opener of a three-game series at Citi Field.

"There are a lot of guys who do a lot of impressive things," said Nationals shortstop Trea Turner, whose bases-loaded walk as a pinch-hitter forced Harper home with the winning run. "He's obviously up at the top of the game with what he (does). So much power, hit to all fields. He's a great player."

Harper's entire offensive arsenal was on display Friday, when the Nationals (11-5) won their fifth straight game.

Harper entered the game just 1-for-26 in his career against Mets right-hander Matt Harvey before greeting Harvey with a monstrous two-run homer beyond the right-centerfield wall.

"You could get dominated your whole life by one guy," Harper said. "Just part of the game sometimes. You do well against a guy and sometimes you don't. Harvey's really good. You never know."

Harper nearly homered down the left field line in his next two at-bats -- one went foul in the third, when he flew out to center, and his drive was caught at the track in the sixth -- before he walked in the eighth.

With one out in the 11th, the left-handed hitting Harper battled Mets southpaw Josh Smoker (0-1) for seven pitches before he doubled down the left field line. Harper took third on a wild pitch by Jeurys Familia and remained there when Anthony Rendon drew a walk before trotting home on Turner's walk.

"Bryce's at-bat, that was a beautiful at-bat, that was a determination at-bat," Nationals manager Dusty Baker said.

The hit was the first for the Nationals since Jose Lobaton's homer leading off the fifth inning.

"Longer that game went on, the harder it was, because we were operating on fumes," Baker said. "That's the one thing that you didn't want was an extra-inning game tonight."

The Nationals were at least equipped for extra innings. The undermanned Mets (8-9), who have dropped six of seven, were missing four Opening Day starters -- first baseman Lucas Duda (left elbow), shortstop Asdrubal Cabrera (hamstring), catcher Travis d'Arnaud (right wrist) and left fielder Yoenis Cespedes (hamstring) -- from their lineup, as well as backup first baseman Wilmer Flores (knee infection). Duda and Flores were placed on the 10-day disabled list Friday.

New York came back from deficits of 2-0 and 3-1 thanks to Michael Conforto, who led off the bottom of the first with a homer, and Curtis Granderson, who delivered an RBI single in the fourth and a homer in the sixth.

Mets manager Terry Collins had to get creative in the late innings, when he used right-handed pitcher Zack Wheeler as a pinch-hitter for Matt Harvey in the seventh. Wheeler doubled but was stranded at third when New York left the bases loaded.

In the ninth, another starting pitcher, Robert Gsellman, pinch-ran for Rene Rivera after Rivera drew a leadoff walk. Cabrera drew a one-out walk as a pinch-hitter, after which he was lifted for pinch-runner Kevin Plawecki. But Gsellman and Plawecki were both stranded in scoring position.

The Mets used every player on their bench except Cespedes.

"You could tell that they were determined over there -- that would have been a big win for them, to play short," Baker said. "It didn't take you very long to see they were banged up and in trouble. But nobody gives you any sympathy in this game. You just have to take advantage of it."

Enny Romero (1-0) threw a perfect 10th inning and Shawn Kelley earned his third save with a perfect 11th. He ended the game by striking out T.J. Rivera, who started at third base hours after being promoted from Triple-A Las Vegas.

"You've got to play with what you have," Harvey said. "And I think we're doing the best we can right now."

Harvey, who was moved up a day when scheduled starter Jacob deGrom was scratched due to a stiff neck, allowed three runs on four hits and two walks while striking out two over seven innings.

"One thing he did (that) we've seen him do in the past -- he battled," Collins said of Harvey. "He didn't have great command of his stuff. He just battled."

Nationals right-hander Tanner Roark allowed three runs on seven hits and three walks while striking out five over 6 2/3 innings.

NOTES: To replace 1B Lucas Duda (left elbow) and IF Wilmer Flores (knee infection) on the active roster, the Mets recalled LHP Sean Gilmartin and RHP T.J. Rivera from Triple-A Las Vegas. Gilmartin could start Saturday if RHP Jacob deGrom (stiff neck) is not ready. ... The Nationals activated SS Trea Turner (right hamstring) from the 10-day disabled list and designated IF Grant Green for assignment.