NEW YORK — The Mets lost again Friday night, blowing two more leads and hearing more boos in an 11-9 defeat to the Seattle Mariners at Citi Field.

New York has dropped 14 of 16 games to fall six games behind the first-place Philadelphia Phillies in the National League East. The Mets are just a half-game ahead of the Cincinnati Reds for the third and final NL wild-card spot.

“It’s part of the mountain,” Mets shortstop Francisco Lindor said. “You got to climb the mountain, and right now, we’re in a very steep part of it. And if we don’t get ourselves together and we don’t push ourselves to be better day in and day out, the mountain is going to be tough to climb.”

The Mets boasted the best record in baseball through June 12, a 45-24 mark that was three games better than everyone else in the NL and 5½ games ahead of the Phillies in the division. Since then, they are 19-34, the second-worst record in the majors over that stretch. Only the Washington Nationals, who fired their manager and general manager this season, have been worse — by just a half-game.

It’s an unnerving scenario after last year’s magical summer, which followed a dismal start to the season and ended with the Mets making an unexpected appearance in the NL Championship Series.

The Mets tasted defeat over the past two-plus months with a variety of recipes. If it’s not a frigid offense, it’s an implosion from the starting pitcher or a costly defensive miscue or a bullpen meltdown or a demoralizing blend of the ingredients. It has left the Mets wondering why they can’t put together enough complete games to resemble the team from the season’s first two-plus months.

“It’s tough,” Lindor said. “We have all asked that question, and it’s tough to point out one thing. We are all trying to win ballgames. All I can think of right now is that we’re not clicking at the same time and the other team is outplaying us.”

The bullpen was the problem in the Mets’ losses the past two nights, a stupefying development after the front office focused on fortifying the relief corps with three marquee relievers before the trade deadline.

“It’s hard to describe, especially with how much talent and elite arms we got back there,” Mets manager Carlos Mendoza said.

On Thursday, the Mets, longing for a solid start from anyone not named David Peterson, received 5 ⅔ good innings from Kodai Senga. But that was wasted when Ryan Helsley, one of those deadline additions, could not hold a one-run lead.

On Friday, the Mets led 6-4 through five innings, but the Mariners pummeled their bullpen with seven runs over the next three frames. Tyler Rogers, another deadline acquisition, surrendered a run in the sixth inning. Seattle scored five runs off Helsley and Brooks Raley in the seventh inning to snatch the lead for good. Frankie Montas, a seismic disappointment demoted to the bullpen this week, yielded the Mariners’ 11th run in the eighth.

“I haven’t seen anything like this,” said Raley, a 37-year-old lefty in his 17th professional season. “Been playing for a long time. But I feel like everybody in here is doing everything they can to show up and play hard, and our offense did that tonight. Those guys were great. Score nine against a team like that, you probably should win the game. I was part of the problem and didn’t get it done.”

After the game, Mendoza repeated what he has communicated to the media in recent weeks — that the Mets are too talented for this slide to continue, that they will turn the tide, that they will start winning again. But just 40 games are remaining in the regular season, and they have been one of the worst teams in baseball for nearly one-third of the schedule. The Phillies are running away with the division, and the Reds are on their heels. Time is running low, and they know it.

“Bottom line, we got to start playing better,” Mendoza said. “Especially when you get the lead, we got to be able to shut those games down. Again, too much talent back there.”