WASHINGTON -- David Wright crossed home plate in the seventh inning and gave an emphatic fist pump toward the ground as reliever Matt Thornton, who had been backing up home, walked near him and back to the mound after giving up a two-out RBI double to Yoenis Cespedes.

Earlier in the inning, Wright had singled in the go-ahead run.

The New York Mets scored three runs in the seventh to take the lead and the bullpen shut the door in an 8-5 win over the Washington Nationals on Monday to extend their lead to five games in the National League East.

"They play with emotion. Sometimes they let it out," Mets manager Terry Collins said.

Collins called Wright an even-keeled guy. But his fist pump showed some emotion to start a key series. Wright returned from a long stay on the disabled list Aug. 24.

"There is no question," Collins said. "It means a lot to have him back. He comes through when you need it."

Meanwhile, Cespedes, the Mets' center fielder, had two doubles, a homer, two runs and two RBIs before a crowd of 34,210 on Labor Day in the nation's capital.

Washington ace Max Scherzer allowed three solo homers and five runs in six innings, though he did not figure in the decision.

"I feel like the arm slot is there. I just have to execute better," said Scherzer, who was handed a 5-3 lead to start the fifth inning. "I'm just disappointed I didn't hold that lead. I have to get the ball down in the zone."

Scherzer has not won at home since June 20 -- a no-hitter against the Pittsburgh Pirates -- and has given up 20 runs in his last five starts.

"It's frustrating," he said. "It starts with me. I know I can pitch better."

The other Washington star, right fielder Bryce Harper, was 0-for-4 and struck out three times -- the last time in the ninth with a runner on base and one out.

"We have to find a way to come back tomorrow," Harper said. "It's already done. I'm over it."

Collins called it the biggest game of the season, and a key acquisition came through for the Mets.

Cespedes had a two-out RBI double off Thornton to highlight the three-run seventh as the Mets took an 8-5 lead. Wright had an RBI single and first baseman Daniel Murphy drove in a run with a sacrifice fly before Cespedes came through with his third hit in a row.

"That is the reason why we went out and got him," Collins said of Cespedes, acquired in a trade with the Detroit Tigers in July. "It is so fun to be around these guys. They don't panic."

The Mets (76-61) improved to 8-6 against the Nationals this year while Washington (71-66) saw its five-game winning streak come to an end at an inopportune time.

The winning pitcher was Dario Alvarez (1-0) while Blake Treinen (2-3) was tagged with the loss. It was the first career win for Alvarez, who appeared in his first game with the Mets this year after four appearances in 2014.

Mets starter Jonathon Niese gave up five runs on seven hits in 3 1/3 innings and has yielded 23 earned runs in his last four starts.

Jeurys Familia pitched the ninth for the Mets to get his 37th save as he fanned Harper and first baseman Ryan Zimmerman.

Zimmerman, shortstop Ian Desmond and third baseman Yunel Escobar had two hits. Mets right fielder Curtis Granderson and shortstop Wilmer Flores, who later moved to second, also had two hits while Granderson also walked twice as the leadoff man.

The Mets grabbed a 2-0 lead in the second on a pair of solo homers. Left fielder Michael Conforto, a rookie, led off with his sixth career homer, and second baseman Kelly Johnson went deep to right with one out.

Scherzer has allowed 24 homers this year after giving up just 18 in each of the previous two seasons with the Detroit Tigers. He has allowed three homers in a game three times this season.

Cespedes lofted a homer just over the reach of Werth in the fourth to give the Mets a 3-0 lead. It was the 13th homer for Cespedes since Aug. 1 and the 18th since the All-Star break.

Washington catcher Wilson Ramos blasted a 1-2 pitch from Niese over the Mets' bullpen in left for a grand slam to give the Nationals a 4-3 lead in the fourth.

Later in the inning, left fielder Jayson Werth (two hits) had an RBI double to make it 5-3. But Scherzer and the bullpen couldn't hold the lead.

The Mets tied the game in the sixth when catcher Travis d'Arnaud had a sacrifice fly to score Cespedes, who had led off with a double and gone to third on a balk by Scherzer.

NOTES: Mets 1B Lucas Duda was activated off the disabled list. He went on the DL on Aug. 22 with lower back soreness. He went 1-for-3 with Double-A Binghamton in a minor league rehab appearance Sunday. ... Mets RHP Carlos Torres left in the fifth inning while favoring his right leg, which he seemed to injure while throwing out CF Michael Taylor on an infield dribbler to the right of the mound. ... Mets RHP Matt Harvey (12-7, 2.60 ERA), the subject of much discussion on a possible innings limit, will face Washington RHP Jordan Zimmermann (12-8, 3.38) in the second game of the series Tuesday. ... New York RHP Tyler Clippard (2-1, 1.27 ERA for the Mets this year) was a member of the Nationals from 2008 to 2014. He was traded from Washington to Oakland in January and then by Oakland to the Mets in July.