WASHINGTON -- Steven Matz had never gone eight innings in a major league start, so it was a pretty tense moment when Bryce Harper came to the plate as pinch hitter with two outs in the eighth on Wednesday afternoon.

The Nationals had two outs and a runner on first base after Clint Robinson, another pinch hitter, singled against Matz after he retired 16 in a row.

"We had Jeurys (Familia) ready," Mets manager Terry Collins said of his closer. "When you have a young player in certain situations, you need to challenge him. That was one of them."

Matz rose to the challenge, retiring Harper on a grounder to end the eighth and Familia retired the side in the ninth after giving up two singles with no outs as the New York Mets beat the Washington Nationals 2-0.

"He has great confidence in his stuff," Collins said of Matz. "He is making big pitches with his fastball. He has great confidence in command of his stuff. He is making big pitches with his fastball. He gets ahead in the count."

Matz improved to 7-1 and lowered his ERA to 2.36 after going eight scoreless innings while allowing just four singles with seven strikeouts and one walk.

"I felt really comfortable on the mound," Matz said. "Rene (Rivera) called a great game. I really credit him. He just had me in a great rhythm."

"He was able to throw multiple pitches for strikes," said Washington second baseman Daniel Murphy, a former teammate of Matz. "He threw the ball really well today. He had a real good feel with his changeup."

Jayson Werth and Ryan Zimmerman, who were both 0-for-3 against Matz, left the clubhouse just minutes after the last pitch and were not available for comment. Harper, who left with Werth, was not in the starting lineup for just the second time this year and his average has fallen to .245.

"Tough lefty," Nationals manager Dusty Baker said of Matz. "This was the day to sit him. Hopefully, this day off will help Bryce for the St. Louis series" that begins here Thursday.

Familia pitched the ninth for his 16th straight save this year and 32nd in a row dating to last year.

Werth and Murphy (two hits) began the ninth with singles before Familia fanned Zimmerman for the first out and got Anthony Rendon on a fielder's choice and then retired Wilson Ramos for the final out on a grounder.

The hard-luck loser was Tanner Roark (3-4), who gave up two runs (one earned) and five hits in seven innings before Oliver Perez took over in the eighth.

"He threw well enough to win," Murphy said of Roark.

The Mets (27-19) took two of three games in the series and have won five of their last six games in Washington. The Nationals (28-19) saw their lead shrink to a half-game over the Mets in the National League East.

Rivera had an RBI single in the seventh off Roark to give the Mets a 2-0 lead. The hit came after Murphy made an error on a ground ball off the bat of Eric Campbell that could have been an inning-ending double play.

"It was not a bad hop. It was a bad play," Murphy said of his error. "It needs to stop. I need to work harder on that."

David Wright hit a solo homer in the first to give the Mets a 1-0 lead. It was the ninth homer in 62 career games at Nationals Park.

Matz made his first career start against Washington.

The Nationals got two runners on base in the second with one out by Danny Espinosa lined to left and Roark flied out to center to end the threat. Mets second baseman Neil Walker had two hits.

"To win a series is huge," Collins said.

NOTES: Mets SS Asdrubal Cabrera came out of the game in the last of the first with back spasms after he was in the starting lineup. He did not bat in the top of the first. INF Matt Reynolds came on to play short in the last of the first and got his first big-league hit in the fifth -- a single to right. ... Washington hitting coach Rick Schu was ejected in the fifth inning after OF Chris Heisey was called out on strikes. ... Mets LHP Steven Matz, the Wednesday starter, entered the game with a mark of 10-1 in 13 regular-season games in the majors. According to Elias Sports Bureau, he is one of two lefties to win 10 of their first 13 starts in the majors. ... Washington RHP Joe Ross (3-4, 2.70 ERA) will face St. Louis RHP Mike Leake (3-3, 4.07 ERA) in the series opener Thursday in Washington. ... The Mets are off Thursday and then host the Los Angeles Dodgers on Friday, with RHP Jacob deGrom (3-1, 3.07 ERA) going against Dodgers LHP Alex Wood (1-3, 4.03 ERA). It was deGrom who beat the Dodgers in Game 5 of the NLDS last October. ... The Nationals' 28-18 start matches the best start in team history, through 2005 when the team moved to Washington. ... Washington 3B Anthony Rendon entered Wednesday with a mark of .367 in his last 12 games, with five doubles, one triple and one homer in 49 at-bats.