Nationals 7, Mets 6 (12): Rookie Bryce Harper lined a two-out single to left field in the 12th inning for his first career walk-off hit as host Washington came back three times, including twice in extra innings.

Ian Desmond went 2-for-6 with three RBIs and Harper finished 2-for-7 with two RBIs as the Nationals took over sole possession of first place in the National League East.

Scott Hairston homered off Ross Detwiler (4-3) to lead off the 12th inning and put the Mets in front 6-5.

Back-to-back doubles by Michael Morse and Desmond made it 6-6. After Desmond advanced to third on a wild pitch, Jesus Flores was intentionally walked before Elvin Ramirez (0-1) walked Detwiler. Xavier Nady grounded into a fielder's choice and Harper drove an 0-2 pitch right in front of a diving Vinny Rottino.

Hairston scored on a wild pitch by Henry Rodriguez in the 10th to put the Mets ahead 5-4 before Washington took advantage of two errors by shortstop Jordany Valdespin sandwiched around a wild pitch by Bobby Parnell to tie the game in the bottom half.

Andres Torres delivered a two-run double in the eighth inning to give New York a 4-3 lead before Desmond tied the game with a two-out RBI single in the bottom half.

David Wright and Valdespin homered for the Mets.

New York's Chris Young made his 2012 debut after recovering from surgery last May to repair a torn anterior capsule in his pitching shoulder. He allowed three runs (two earned) and six hits in five innings with a fastball in the low to mid-80s.

Washington’s Jordan Zimmermann allowed two runs, five hits and struck out five in six innings, and went 2-for-2 with a double and a run scored.

GAME NOTEBOOK: Wright scored his 736th career run to move past Jose Reyes and into first on the Mets’ all-time list. … Young went 1-0 with a 2.35 ERA in four rehab starts. … Zimmermann is 0-3 in six starts at Nationals Park in 2012. … Morse had his first two hits of the season in his third game after recovering from a strained lat muscle.