"Those guys who have been here all year long and we've asked them to do tough jobs, they deserve to be treated with respect," said Mets manager Terry Collins. "We have a good ballclub here and we're going to show people what we're made of."
Mike Pelfrey started the game for New York but was pulled after 4 2/3 innings. He gave up three runs on five hits with five walks while Ryota Igarashi (3-1) got the win for getting the final out of the fifth.
Danny Espinosa went 3-for-3 with an RBI and a run scored while Wilson Ramos added two hits and an RBI for the Nationals, who have dropped four of their last five.
Livan Hernandez (8-13) was tagged with the loss in his final start of the season and possibly his career. He gave up six runs on eight hits in 5 1/3 innings and failed in a chance to move to .500 in his career as he fell to 174-176 over his 15 full seasons in the majors.
"I've had a real good time here and a real good time playing baseball," said Hernandez. "I've gotten so much support through my career and this is the greatest job to have."
It was his 474th consecutive appearance as a starter and he will be shut down for the rest of the season to make room for returning phenom Stephen Strasburg and other youngsters to allow them time in the rotation.
The Mets grabbed the initial lead in the third inning when Tejada hit a single to right that scored Josh Satin and Mike Nickeas.
Washington, though, responded with a three-run fourth. Jayson Werth walked and Rick Ankiel singled to start the inning and Espinosa brought home Werth with a double. Chris Marrero then grounded out to chase home Ankiel and Ramos doubled in Espinosa for a 3-2 lead.
After Washington left the bases loaded in the fifth, a four-run sixth inning put the Mets back on top. With one out, Duda tied the game with his ninth home run of the season. Later in the frame with the bases loaded and Todd Coffey on the mound, Harris hit a two-run single and Nickeas laid down the suicide squeeze that scored Jason Bay for a 6-3 advantage.
Bobby Parnel worked around a two-out walk in the ninth inning to get his fifth save of the season.
The Mets have won eight of the 14 games against the Nationals this season...Desmond had his eight-game hitting streak snapped thanks to an 0- for-5 day while Ramos extended his hitting streak to eight games...David Wright of the Mets went 2-for-4 with a run scored to move his hitting streak to eight games...The Nats welcome Los Angeles for four games starting on Monday...The Mets play three games in Florida beginning on Monday.