NEW YORK (AP) -- As bad as his back felt Thursday, Davey Johnson was all smiles after what most likely was his final trip to New York as a big league manager.
His Nationals made it real easy for him to grin.
Ryan Zimmerman, Adam LaRoche and Wilson Ramos homered off Aaron Harang in his Mets debut, and Washington beat New York 7-2 Thursday to complete a four-game sweep.
''A lot of fun, a lot of fun,'' Johnson said. ''A lot of good things all around.''
The 70-year-old, who is retiring after the season, led the Mets to the 1986 World Series championship and he said he enjoyed his time in the organization, not only with the big league club but also while managing in the minors. He tried to loosen up his back by walking in the outfield before batting practice.
While reminiscing about his days at old Shea Stadium, Johnson switched to the present, saying: ''It would make my day if we sweep them here - it would make my year.''
And the Nationals obliged, with another power display.
Anthony Rendon also connected for Washington, which outhomered the Mets 13-0 in a series that helped the Nationals remain on the fringe of the NL wild-card race. They moved within 5 1/2 games of idle Cincinnati for the final spot with the rain-interrupted win.
''We're in a place now where we got to win. Usually when you playing that type of baseball where you're forced to win, you either do or you don't. We'll see what happens the rest of the way.''
Zimmerman added an RBI double in the eighth after Denard Span extended his career-best hitting streak to 23 games with a leadoff double. The Nationals won 17 of those games.
''It's fun having a guy like that at the top of the order,'' Zimmerman said.
The Mets have lost nine of 11 and fallen to 64-81, ensuring their fifth straight non-winning record - all at Citi Field.
''There are expectations that come when you're a big league player. And part of those expectations is the ability to execute when you need to. And we're not doing that right now,'' Mets manager Terry Collins said.
Tanner Roark (6-0) allowed two runs and six hits in six innings of his second big league start. Roark pitched six scoreless innings Sunday against Miami.
Johnson said if the 56-minute delay had gone more than an hour, Roark wouldn't have come back in the second inning.
With the win, Roark became the first player in the franchise to win his first six decisions since Jeff Juden in 1996-97 for Montreal.
''After the third inning, I settled down,'' Roark said. ''Offspeed and slider really worked today.''
New York signed Harang (0-1) to a minor league deal on Sept. 1, less than a week after the team learned ace Matt Harvey had a partially torn ligament in his pitching elbow. Harang allowed the three homers and a single in six innings, struck out 10 and walked one. The right-hander was 5-11 with a 5.76 ERA in 22 starts this year for the Seattle Mariners.
''I felt good with throwing some of my pitches,'' Harang said. ''Besides really the two mistake pitches I felt really good about my day.''
It was all or nothing for the Nationals against Harang until Bryce Harper singled to center with two outs in the sixth. Harang gave up only the three homers and struck out 10 before Harper's hit. Span was the only Nationals player that spent any time on the bases - he walked with one out in the third.
Zimmerman homered for the eighth time in 10 games with one out in the first, a drive to straightaway center. The Mets evened the score on Daniel Murphy's RBI double in the bottom half.
After the delay, LaRoche hit a drive to left-center that Eric Young Jr. appeared to knock back into play with a leap at the wall. But after a video review of more than three minutes, umpires ruled a home run that gave Washington a 2-1 lead. It was LaRoche's fourth homer in 32 at-bats against Harang.
The Mets tied it again on Anthony Recker's RBI single to left field in the fourth. The Mets might've run themselves out of a big inning when Mike Baxter was thrown out trying to advance to third on the play.
Ramos homered leading off the fifth to put Washington ahead for good. After Recker's hit, Roark retired seven of his final eight batters.
New York had runners on second and third in the seventh but Craig Stammen struck out Juan Lagares to end the chance. Rendon hit a sacrifice fly in the seventh and homered in the ninth.
NOTES: The Nationals' 13 homers were a record for a single series at Citi Field. The Yankees hit seven in 2012. ... Double-A Binghamton manager Pedro Lopez joined the Mets as a coach. He guided Binghamton to 86 wins and a trip to the Eastern League playoffs. ... The Nationals will hold a ceremony to honor the victims and first responders of Sept. 11, 2001, on Friday, when Washington opens a 10-game homestand against Philadelphia.