WASHINGTON -- New York Mets manager Terry Collins played a hunch Tuesday, giving rookie T.J. Rivera a rare start at second base.

With Wilmer Flores still banged up, Collins turned to a rookie who made his big league debut at third base on Aug. 10 and had just 41 at-bats in 16 games before Tuesday.

Rivera, 27, a native of The Bronx, came through in a big way. He went 3-for-4 and hit a solo home run in the 10th inning as the Mets beat the Washington Nationals 4-3 to keep their wild-card hopes alive.

The blast off Washington closer Mark Melancon (2-2) was the first career homer for Rivera.

"That doesn't happen very often," Collins said of Melancon getting taken deep. "That was huge for us."

Rivera also drove in three runs.

"Fortunately he came through with a huge night," Collins said of Rivera, who hit .349 in the minors last season. "He takes what they give him."

Former Washington pitcher Jerry Blevins fanned Daniel Murphy, a postseason hero for the Mets last October, for the final out in the 10th with a runner on base. Blevins recorded the third save of his career, his first since 2012.

The second-place Mets (77-68) are nine games back of the first-place Nationals (86-59) in the National League East. New York will aim for its seventh straight series win Wednesday.

The Nationals scored two runs in the ninth on RBI singles by Anthony Rendon (two hits) and Wilson Ramos (two hits) to tie the game at 3-3.

"He is not chasing bad pitches," Washington manager Dusty Baker said of Ramos, who had been mired in a slump.

Baker had some choice words with plate Hunter Wendelstedt late in the game but was not ejected. Was Baker trying to fire up his team?

"That is not my purpose. That was not my effect," Baker said.

The Mets turned a double play to end the ninth inning with two runners on base against closer Jeurys Familia (3-3), who picked up the win after blowing the save.

"He was frustrated by it," Collins said of Familia, who fell to 48-for-42 on save chances.

Mets starter Noah Syndergaard allowed one run and four hits in seven innings, striking out 10 and walking one. James Loney, Rene Rivera and former Nationals infielder Asdrubal Cabrera had two hits apiece for New York.

Murphy had a one-out double in the sixth to give him at least one hit in all 18 games against his former team this season. He added an infield single to start the ninth.

Syndergaard lowered his ERA to 2.43.

"I made a slight adjustment in my mechanics the other day," said Syndergaard, who used a two-seam fastball to try to establish the inside part of the plate.

The tall right-hander has 205 strikeouts this season, and his fastball hit triple digits on the stadium radar gun several times. He has fanned at least 10 batters in five games this season, but Tuesday was the first such outing since June 15.

Ramos' RBI single with one out in the first scored Harper to give the Nationals a 1-0 lead against Syndergaard. Ramos entered the game with only three hits in his previous 19 at-bats.

The Mets tied the game at 1-1 in the third as Rivera had an RBI single with two outs to score Cabrera, who led off with a double.

Curtis Granderson had an RBI triple in the fifth for the Mets, and Rivera came through again with a sacrifice fly off A.J. Cole to up the margin to 3-1.

The Washington starter allowed nine hits and three runs with two walks and six strikeouts in five innings.

NOTES: Washington RHP Tanner Roark (14-8, 2.85 ERA) pitches Wednesday against New York RHP Robert Gsellman (2-1, 3.92 ERA) in the series finale. ... Mets LHP Steven Matz (shoulder), who has not pitched since Aug. 14, was supposed to throw Tuesday in Florida but rain postponed that until Wednesday, according to manager Terry Collins. Matz and RHP Jacob deGrom (forearm inflammation), who has not pitched since Sept. 1, could figure into the spot in the rotation after RHP Rafael Montero gave up six runs in less than two innings Monday, Collins said. ... Washington manager Dusty Baker did not have any updated information on RHP Stephen Strasburg, who left his start Wednesday after 42 pitches with a flexor mass strain. ... Collins said he spoke with former Mets infielder Wally Backman, who announced Monday he will not return as the Triple-A Las Vegas manager in the New York system. "I have always admired him. I hope the best for him," Collins said of Backman, who played on the 1986 World Series team.