"I just couldn't get into a rhythm, fell behind, wasn't able to execute pitches when I needed to," Niese said. "When that happens it's tough for the defense to stay on their toes when I'm working behind."
In the third, Hairston doubled home Ramos and scored on a single by Moore to make it 5-0.
Following consecutive shutout losses to the Yankees the Mets finally broke through against Roark.
Lucas Duda opened the fifth with a single and Anthony Recker doubled. Duda scored on a groundout by Ruben Tejada and Young's double brought home Recker to pull New York within 5-2.
The game was delayed briefly when a fan came onto the field near the Nationals' dugout and ran from first base around to home with one out in the ninth. He was tackled hard by a security person just behind home plate, drawing cheers from the crowd.
NOTES: Washington selected the contract of 1B Greg Dobbs and optioned C Sandy Leon to Triple-A Syracuse prior to Friday's game. Dobbs, released by the Marlins on May 6, was signed as a minor league free agent Monday. To make room on the 40-man roster, the Nationals put Syracuse outfielder Eury Perez (broken toe) on the 60-day DL. . Manager Matt Williams said two Nationals on the DL, LF Bryce Harper (left thumb strain) and 3B Ryan Zimmerman (right thumb fracture), have doctor appointments next week and will get progress reports. . Mets RHP pitcher Jenrry Mejia, being eased into the closer's role, was unavailable after pitching the ninth inning Thursday night. "He hasn't been back-to-back in four years, so we've got to be careful," Collins said, adding Mejia will pitch consecutive games soon. . New York's Bartolo Colon (2-5, 5.84) opposes Gio Gonzalez (3-3, 3.97) Saturday.