NEW YORK -- Seth Lugo didn't come out of nowhere, and neither did the New York Mets. But neither Lugo nor the Mets look ready to return to their meager roots anytime soon.

Lugo continued to serve as an unexpected stopper for the Mets on Sunday night, when the rookie right-hander earned the win after allowing one run over a career-high seven innings as New York kept pace in the National League wild-card race with a 5-1 victory over the Washington Nationals at Citi Field.

The Mets (71-66), who won the final two games of the three-game series, are one game behind the St. Louis Cardinals in the race for the NL's second wild card. New York is 10-5 since Aug. 19 -- the day Lugo entered the rotation and took the loss against the San Francisco Giants as New York fell a season-high two games under .500 and 5 1/2 games behind the Cardinals.

"They've taken a lot of beatings this summer with all the things that have happened," manager Terry Collins said of the Mets, who have lost five Opening Day starters to season-ending injuries. "We're going into September and we're in a pennant race. That makes September a lot of fun and they're making it fun."

Nobody has delivered more unexpected smiles for the Mets than Lugo, who had a 6.50 ERA in 21 games (14 starts) at Triple-A Las Vegas this season and appeared as a reliever in nine games -- eight of which New York lost -- between July 1 and Aug. 17 before being tabbed to replace injured left-hander Steven Matz in the rotation.

All Lugo has done since then is go 3-1 with a 2.19 ERA in four starts. He exited to a standing ovation Sunday after allowing six hits and no walks while striking out four and throwing 73 of his 101 pitches for strikes.

"Pretty awesome," Lugo said. "Adrenaline was definitely going. That was great. A lot of fun."

Lugo wriggled out of a bases-loaded jam in the first inning Sunday and retired 11 straight between the second and fifth. He allowed leadoff singles in the sixth and seventh before retiring the next three batters each time.

"I think he's gotten stronger because he's lengthened himself out a little bit," Collins said. "(The seventh) inning was a big inning for him. I thought that was an inning (where) hey, look, you've got to go out and get us through this."

Lugo said a brief trip back to Las Vegas -- he was with the Triple-A club from Aug. 2 through Aug. 12 -- reminded him he could succeed in the majors.

"Went down there and helped take a little pressure off of me and tell myself those are just some hitters at the plate, not to look at the name on the back of the jerseys," Lugo said.

Addison Reed and Jeurys Familia threw a scoreless inning apiece to close out the win for the Mets, who limited the Nationals to six runs in the series.

Curtis Granderson produced the Mets' first three runs Sunday with a sacrifice fly in the first inning and a two-run homer in the third inning. Jay Bruce added a two-run homer in the sixth inning.

"They have good pitching -- it's their strength -- and they're hitting the ball out of the ballpark," Nationals manager Dusty Baker said. "And they did both of those two against us."

Danny Espinosa homered in the second inning and Jayson Werth had two hits for the Nationals (79-57), who lead the Mets by 8 1/2 games in the NL East and are three games ahead of the NL West-leading Los Angeles Dodgers in the race for the second seed in the NL.

"I still believe that we haven't hit our stride yet -- I mean, every team has won seven, eight, nine, 10 in a row except us," Baker said of the Nationals, whose longest winning streak of the season was a seven-game run in April. "So I still believe our best time of the year is yet to come."

Rookie right-hander Reynaldo Lopez (2-3), who was recalled from Triple-A Syracuse in order to give Max Scherzer an extra day of rest, took the loss after allowing three runs on six hits and one walk while striking out three over four innings.

NOTES: Both the Mets and Nationals wore first-responder hats during batting practice before the Mets' final home game before Sept. 11. The Mets will also wear the hats during batting practice when they visit the Atlanta Braves on Sept. 11. ... Nationals RHP Max Scherzer and Mets RHP Bartolo Colon, who are scheduled to pitch against the Braves and Cincinnati Reds, respectively, on Monday afternoon, traveled ahead of their teammates to Washington, D.C., and Cincinnati. ... Mets manager Terry Collins said RHP Jacob deGrom (right forearm) is likely to miss at least two starts. ... Nationals RHP Stephen Strasburg (sore right elbow) had another successful bullpen session. He could return to the rotation on Wednesday.