WASHINGTON -- You might think 19-year-old Bryce Harper would savor the moment after his first game-winning hit with two outs to give his team an extra-inning win.
"I'm happy to get the W, of course. I'm happy to get that walk-off hit, but I don't like going 2 for 7," Harper said. "I don't like striking out twice in one game, either."
He then said the game-winner would mitigate his disappointment.
"To get that moment at the end, that wipes everything away," Harper said.
Harper's single ended a back-and-forth game that saw the Mets rally from a 3-0 early deficit to take leads in the top of the eighth, 10th and 12th innings -- only to have the Nationals tie the game in the bottom of the frame each time.
Scott Hairston hit a solo homer in the top of the 12th to give New York a 6-5 lead, but the Nationals rallied when Michael Morse led off with his second double of the game. Ian Desmond followed with another double for his third RBI.
Reliever Elvin Ramirez (0-1) walked two batters to load the bases, and a fielder's choice by Xavier Nady left the bases loaded with two outs for Harper, who lined an 0-2 pitch to left field. The ball fell just in front of a diving Vinny Rottino.
"He's a man-child," Morse said of Harper. "This guy's unbelievable. He's really learning this game. Every day, I think he's taking something in. ... When he plays like he plays, it's fun to watch and it's good to have him on our side."
The Nationals are alone atop the National League East, a game ahead of Miami -- which lost to Atlanta -- and 1 1/2 games ahead of the Mets.
Both managers emptied their bullpens as the game wore on. Ramirez, the Mets' sixth pitcher, was making his second major league appearance. Ross Detwiler (4-3) pitched the final two innings as the Nationals' eighth.
"It would have been very easy for this team, for the hitters, to just say, 'OK, we'll just go get them tomorrow,'" Detwiler said. "But we weathered the storm, we came back out there and fought."
Hairston also gave the Mets the lead in the 10th when he led off with a single and later scored on a wild pitch by Henry Rodriguez -- Rodriguez's ninth in 21 innings this season. The Nationals tied it in the bottom of the inning, thanks to two errors by shortstop Jordany Valdespin -- including a grounder by Desmond that bounced off his glove, allowing Ryan Zimmerman to score -- and a wild pitch by Bobby Parnell.
The Mets fell behind 3-0 after five innings and started their comeback with solo home runs by David Wright and Valdespin in the sixth. Andres Torres hit a two-run double in the eighth to give New York a 4-3 lead.
Desmond tied the game at 4 with a run-scoring single in the eighth to set up extra innings.
Valdespin led off the sixth with a pinch-hit home run into the Nationals' bullpen in right field. It was the rookie's second pinch-hit homer this season. Wright added another solo homer with two outs, barely clearing the wall in left-center field. It was Wright's 736th career run scored, setting a Mets franchise record.
"The toughest part is the way we fought back," Mets manager Terry Collins said. "You're down three. We fight back. We get the lead. We lose the lead, get the lead, lose the lead, we get the lead and then we lose the game. That's very tough. The guys played very well."
According to the Nationals, Harper is the first teenager to have a game-ending hit since Gary Sheffield did it for the Brewers on Sept. 9, 1988.
"I don't think of him as a 19-year-old kid, but that's exactly what he is," Detwiler said. "He's going to be around for a long time, so it's awesome to see him learn and really grow as a player right now. You know he's going to be in the same position he's in now in 10, 15 years. It's pretty cool to see the beginning of it."
New York RHP Jon Rauch has "debris" in his right elbow, according to manager Terry Collins. He'll miss the three games in Washington, but will be available for Friday's game against the Yankees, Collins said. ... The Mets activated RHP Miguel Batista (lower back strain) from the 15-day DL and placed RHP Ramon Ramirez (strained right hamstring) on the 15-day DL. Ramirez injured the hamstring running in from the bullpen to join in the celebration of Johan Santana's no-hitter on Friday, Collins said. The Mets also designated right-handed pitcher Jack Egbert for assignment. ... Washington RHP Brad Lidge (sports hernia) made his first rehab appearance for Class A Potomac Monday and expects to have two more on Wednesday and Friday.