Mets manager Jerry Manuel promised changes after his bullpen collapsed again yesterday, and wasn’t ruling anything out.

“I might start using starters down there,” he said with a grin.

Steve Pearce hit a two-out, two-run single in the ninth inning and the Pittsburgh Pirates became the latest team to take advantage of the Mets’ slumping relievers, rallying for a 7-5 win.

“We can’t continue to perform this way late in the game,” Manuel said. “We have to make some adjustments. I have to figure out what I have and who is willing to step up in those roles.”

The Mets led 5-1 when Pedro Martinez left after six innings, but five relievers couldn’t preserve the edge. The Pirates, in town to play a makeup game, scored three times in the seventh and three more in the ninth.

“Today was a big win for us, a big win,” said Ryan Doumit, who atoned for an earlier error with a tying RBI single in the ninth. “They had the momentum the entire game.”

It marked the ninth time this season New York lost a game in which it led in the eighth inning or later. The Mets have struggled lately minus injured All-Star closer Billy Wagner.

“This is obviously a tough one to swallow,” third baseman David Wright said. “We have to refocus and not allow this to cross over into this road trip.”

Aaron Heilman (2-7) began the ninth with a 5-4 lead, but allowed four straight Pirates to reach after striking out leadoff hitter Nate McLouth. Doumit hit a tying single off the right-center wall and Heilman hit Andy LaRoche with a pitch to load the bases.

Scott Schoeneweis relieved and got Brandon Moss to ground into a forceout at the plate. Pearce followed with his tiebreaking single to center.

“I didn’t want to let the team down like I did previously,” said Pearce, who committed a baserunning blunder in the third and popped up with the bases loaded to end the fourth. “I got in there, worked the count and got the pitch that I was waiting for.”

Heilman absorbed his third blown save in five opportunities and is 1-4 with a 10.97 ERA in his last nine games.

“You just keep pitching,” Heilman said. “You just keep going out there and keep battling. It’s all you can do.”

Carlos Beltran hit a leadoff single in the bottom half after Manuel was thrown out by umpire Bill Hohn for arguing balls and strikes. But John Grabow struck out Carlos Delgado and got Fernando Tatis to ground into a double play.

Denny Bautista (4-1) worked a scoreless eighth for the win and Grabow earned his second save.

“It was real big for these guys to really pull together and come back,” Pirates manager John Russell said, “especially 5-1 down, and didn’t look like anything was going our way at all.”

New York wasted an effective start by Martinez, who allowed one run and three hits. Wright hit a three-run shot and Robinson Cancel had his first career homer.

Doug Mientkiewicz had three hits and drove in two runs for Pittsburgh, which held second baseman Freddy Sanchez and shortstop Jack Wilson out of the starting lineup because of minor shoulder problems.

Sanchez had a pinch-hit RBI double as the Pirates pushed across three runs in the seventh to cut it to 5-4. The Mets used Joe Smith, who failed to retire both batters he faced, Pedro Feliciano, and Duaner Sanchez to get through the inning.

Sanchez got the final out and worked a scoreless eighth before the implosion in the ninth.

The Mets got off to a fast start against Zach Duke. Jose Reyes led off the first with an infield single, Nick Evans reached on third baseman LaRoche’s error and Wright hit his 23rd home run.

The Pirates’ defense hurt them again in the third. Cancel hit a two-out single to center and McLouth made a nice throw to the plate but Doumit dropped it, allowing Delgado to score.

“That play was unexcusable,” Doumit said. “It was a perfect throw from Nate.”

Cancel, getting the start behind the plate with Ramon Castro ailing, homered in the sixth.

The Pirates and Mets started late when the game, a makeup of an April 28 rainout, was delayed 31 minutes because of rain in the area of Shea Stadium. The first few innings were played under overcast skies that eventually gave way to a sunny afternoon.