NEW YORK -- A three-run first inning and a short start by Padres ace Jake Peavy are typically causes for celebration.

"I think everybody would have said that's mission accomplished," third baseman David Wright said.

But with Peavy on the ropes, Thursday's crowd of 35,985 watched as the Mets could not deliver a fatal blow, letting the Padres hold on to a lead gained through a five-run third inning en route to a 6-5 win to secure the series.

"We continue to put ourselves in a good position," manager Jerry Manuel said. "We just haven't been able to finish it at this point."

It wasn't that the Amazin's lacked any fight. With a chance to christen Citi Field with its first series win, the Mets jumped on Peavy from the get-go.

Jose Reyes hit a game-opening single off the 2007 Cy Young Award winner and Daniel Murphy followed with a walk. A balk call with Carlos Delgado batting advanced the runners, but it hardly mattered, since Delgado smashed the ensuing 3-0 pitch over the right-center-field fence. The blast traveled an estimated 440 feet and extended Delgado's hit streak to 14 games, dating back to Sept. 24, 2008.

Peavy's 44-pitch first inning had the right-handed ace in an unusual position: vulnerable.

With one out in the fourth, the Mets continued to push Peavy's pitch count and apply steady pressure. Reyes beat out a potential inning-ending double-play ball, which was followed by Murphy's ground-rule double down the left-field line.

But Peavy didn't crack, and got Wright to strike out looking to thwart the Mets' attack.

"That's why he is who he is," Manuel said of Peavy. "Despite his struggles and our battle with him, he never really gave in.

"I thought we had some chances ... but he kept hanging in there making plays."

Peavy didn't allow another hit and exited after five innings, with Delgado's three-run knock his only blemish.

But the Mets' early cushion wasn't enough for right-hander John Maine. After cruising through the first two frames with barely a hiccup, Maine opened the third with a walk to Henry Blanco. Three of the next four Padres connected for a base hit, then San Diego batted around the order and worked Maine for a 46-pitch, five-run inning.

It was a frustratingly familiar story for Maine, who has struggled with inconsistencies within his starts.

"It just seems a lot of time it's just one inning that does me no good in a game," said Maine, who was visibly upset as he stood in front of his locker.

Although the Padres collected just one extra-base hit, all three of the batters Maine walked -- one intentionally -- went on to score.

"He was just behind hitters a lot," catcher Ramon Castro said. "When you get behind the hitters, that's what happens."

After pitching around Adrian Gonzalez in the third inning, Chase Headley made Maine pay for it with a two-out, two-run double. Headley finished the night with four hits and three RBIs and was a source of irritation for Maine, who denied that his increased velocity has made his fastball more difficult to maintain.

"I mean, it's just frustrating. I made some good pitches, and they just hit it and put it in play," Maine said. "I just couldn't get a ball to go by somebody, and it's just frustrating."

Frustrating, in fact, aptly describes Thursday's narrow loss.

"It seems like one inning there is killing us," Wright said. "We are playing seven or eight good innings, but then there's one or two innings where we just kind of take a little detour."

The Mets' offense tried to right the ship in the eighth inning, when the red-hot Ryan Church opened with a single and Castro connected for a two-run blast, sending a 2-1 pitch over the left-field fence to put the Mets within one run.

Veteran slugger Gary Sheffield came on to pinch-hit and drew a one-out walk to put the tying run on base, but Padres reliever and former Met Duaner Sanchez got Reyes to ground into an inning-ending double play.

"They came through when they needed to," Maine said. "They had guys in scoring position. Even with two outs, they did it."

On Thursday night, that made all the difference.