NEW YORK — Daniel Murphy keeps turning those Citi Field boos into booms.

Murphy hit his seventh home run this year against the team that let him go last winter, lining an early drive off the facing of the upper deck and leading the Washington Nationals over the New York Mets 3-2 Sunday.

"That guy's the real deal. He's definitely a cyborg right now," winning pitcher Gio Gonzalez said.

"You don't know what to throw him," he said. "You might have to throw him pingpong balls."

Murphy tops the majors with a .348 batting average at the All-Star break, boosted by the damage he's done to the Mets. He homered three times and drove in 10 runs as the NL East leaders took three of four in this series, opening a six-game edge over New York.

Murphy, as usual, deflected any notion he's the main reason his team is soaring.

"Carry it? No, no, no," he said. "The list is too many. Just a small piece of it."

As for his own impressive first half that includes 46 extra-base hits and 66 RBIs?

"I would say I'm surprised," Murphy said.

Murphy connected in the first inning for his 17th homer this year. Overall, he is 22 for 52 (.423) with 21 RBIs vs. his old club.

"I don't think it's just against us. He's hitting like .350," losing pitcher Steven Matz said.

"I don't have any answer," he said.

If there's any consolation for Mets manager Terry Collins, he'll soon have Murphy back on his side, albeit for just a day — Collins is guiding the NL team in the All-Star Game on Tuesday night in San Diego, and Murphy is on the squad.

The Nationals posted their 54th win, matching the 1994 Montreal Expos for the most in franchise history before the break.

"Very pleased with the first half we had," said first-year Nationals manager Dusty Baker. "We know we can get even better."

Jose Reyes hit two home runs for the Mets, including a leadoff shot in the first inning. He connected in his first two at-bats, then took three wild swings his next time up and struck out.

Gonzalez (5-8) pitched into the sixth as the Nats won their third straight against the Mets and beat them for the ninth time in 13 matchups this year. The lefty had lost seven of his previous eight decisions, but regained his touch in a ballpark where he's now 8-1.

Tanner Roark made his first relief appearance of the season, replacing Gonzalez and retiring seven straight batters. He went seven innings last Wednesday for a win.

Jonathan Papelbon pitched the ninth for his 19th save in 21 chances. His 368th career save moved him past Jeff Reardon into ninth place on the all-time list.

Matz (7-5) fell to 0-4 in his last eight starts. He gave up an RBI single to All-Star Wilson Ramos in the third that put Washington ahead 3-1, and left after the seventh.

It took Murphy less than two months to go from valued ex-player to villain at his former home. Murphy drew two standing ovations and got a video tribute when he returned for the first time in mid-May.

The longtime second baseman whose playoff slugging helped the Mets reach the World Series last year got jeered every time he came to the plate on this afternoon. He managed to make at least one new fan, however — after chasing down a popup that landed in foul territory, he pointed to a young person in the stands and tossed the souvenir that way.

TRAINER'S ROOM

Mets: OF Yoenis Cespedes (strained right quadriceps) hasn't started since getting hurt Friday night. Collins said it was unlikely the slugger would've been able to pinch-hit. ... OF Alejandro De Aza twice knocked himself down with foul balls in the fourth. He got checked and stayed in.

LOOKING AHEAD

Nationals star Bryce Harper has played vs. every opposing team in the majors except Cleveland, but could see Indians pitcher Corey Kluber in the All-Star Game — in the next month, the Nats take on Cleveland four times. Major league wins leader Chris Sale could start for the AL, and Harper has faced him once, in the 2013 All-Star Game at Citi Field. "Lined out to third," he remembered.

UP NEXT

Nationals: Open a nine-game homestand next Friday, starting with Pittsburgh. The Dodgers and Padres later visit Washington.

Mets: Start a three-game series at Philadelphia on Friday. RHP Noah Syndergaard, who left his last start with arm fatigue, will pitch at the back end of the rotation coming out of the break, Collins said.