Mets’ good vibes will end if David Stearns can’t fix this thorny issue

The good times at Citi Field began to melt one walk at a time. All of the positive vibes launched by a furry purple mascot, an unexpected hit song and — of course — lots of winning reversed in the eighth inning Saturday when the soundtrack devolved from “OMG” to the more familiar “boo.”

The targets were Jake Diekman and Reed Garrett because, well, they could not hit their targets. Each walked the first two batters they faced. Three of the free passes scored. They threw so many balls that at one point the umpires embarrassingly lost semblance of the count, thinking that there were three balls on pinch-hitter Trey Cabbage when he actually already had walked.

That was rectified by replay.

David Stearns is going to have a much tougher time fixing the bullpen issue.

With a chance to go two games over .500 and tie the Cardinals for the final NL wild-card slot, the Mets instead blew what had been an early five-run lead and returned the Grimace to the facial expression of their fans.

“Four walks in the eighth inning, they are going to make you pay, especially a team with that kind of offense,” manager Carlos Mendoza said.

Mendoza was operating with a thin staff. He is playing one man down without the suspended Edwin Diaz. Even in victory Friday, Jose Quintana provided just four innings, leaving four relievers to cover five innings. So Mendoza stuck with Tylor Megill through a three-run fourth, but Megill bulged his pitch count by walking three of the final seven hitters he faced for a Mets staff that has walked the highest percentage of hitters in the majors.

Ty Adcock, picked up on waivers in May and promoted Wednesday, provided 1 ¹/₃ shutout innings after Megill left with one out in the sixth. The key for Diekman with a two-run lead was to work though the less-fierce part of the Astros lineup, but he walked Jake Meyers and Jeremy Pena protecting a 6-4 lead in the eighth. Garrett — a revelation, but a heavily used one — walked two, threw a run-scoring wild pitch and after getting ahead 0-2 on Alex Bregman, worked the count full before yielding a go-ahead, two-run single.

Both Diekman and Garrett were booed off the mound; so was Danny Young after permitting two ninth-inning insurance runs. It was distant from the euphoric dance party that broke out when Jose Iglesias sang “OMG” after the game Friday night. But it was a familiar beat from this season — too many bases on balls.

Even as the mood brightened around the Mets the past three weeks, it had become understood that if this run of success reflected a true contender, then the ’pen would have to be fixed. In part because Mets relievers just walk too many hitters — 10.4 percent entering the second game of this series. And the stuff is just not dominant enough to survive so many free passes and poor counts.

The Mets know they are down Brooks Raley and Drew Smith for the season, and have no clue what they have mentally or physically in Diaz, who can return from his ban for sticky stuff on July 6.

Stearns has tried shuffling already and is not done. Once Christian Scott is recalled and Kodai Senga gets healthy and returns — and Mets officials are more optimistic about that now than any other time this season — Megill and/or David Peterson can be transitioned to the ’pen and see if their stuff plays up.

The Mets are liking Triple-A reports on lefty Tyler Jay and righties Max Kranick and Eric Orze.

But the Mets have protected and added to their system enough in the last two years to be aggressive between now and July 30 at 6 p.m. to add two more legitimate relief arms.

Would the Mets like more starting pitching? Sure. Who wouldn’t? But the market is going to be thin and to give up significant prospects you would have to believe the addition would be part of a postseason rotation, and the Mets are uncertain that this thin market will offer a no-doubt upgrade on Senga, Scott, Sean Manaea and Luis Severino.

They have more concerns about how long Starling Marte will need to heal from a bone bruise of his right knee — and what they will have when he does return. Stearns liked Tyrone Taylor with the Brewers and is curious what level of production will manifest with a month of regular play. Again, the Mets will monitor if the market actually can clearly bring something better.

The ’pen is more of a no-brainer. It has pitched better as the Mets climbed from 11 games under .500 to one over by winning the first game against the Astros on Friday night. But the Mets returned to break-even Saturday, blowing a 6-1 lead, turning the good mood sour and reminding everyone that “OMG” is easy for Stearns. It will come down to how he spells R-E-L-I-E-F.