Mets relief pitcher Seth Lugo stands on the mound after...

Mets relief pitcher Seth Lugo stands on the mound after giving up a grand slam to the Marlins' Jerar Encarnacion during the seventh inning of an MLB game at Citi Field on Sunday. Credit: Kathleen Malone-Van Dyke

There should be very few occasions when the best team in the National League is booed at its home ballpark, if at all.

Sunday was one of those rare times, Seth Lugo being the primary recipient in the Mets’ 6-2 loss to the Marlins.

Just Lugo’s luck, it was a Father’s Day crowd, more than 41,000 strong at Citi Field, and the fans were not thrilled to have a potential fourth straight victory swiped from them in the seventh inning.

Called on to protect a 1-0 lead with the bases loaded, Lugo left a full-count sinker up to Marlins rookie Jerar Encarnacion, who smacked it over the rightfield wall for a grand slam. Encarnacion, who began the season at Double-A Pensacola, was making his MLB debut, and he circled the bases like a Little Leaguer — pointing to the sky, pumping his fists, wired on adrenaline.

That brought an avalanche of boos down upon Lugo, and the Citi Field jeers continued throughout the seventh after Jon Berti’s RBI double and as Lugo walked off the field at the inning’s end.

“It’s part of the game, you know?” Lugo said. “I’ve been here a long time and it’s always been a thing here so — it just is what it is.”

Hey, the Citi Field fans are a demanding bunch. As Lugo mentioned, that’s nothing new. Boos can be as much a part of the Flushing soundtrack as the Delta shuttle buzzing by overhead. It was just a bit more shocking to hear them quite that loud Sunday.

 

Lugo blew it. There’s no sugarcoating his performance. And to tee that pitch up to a rookie after falling behind 1-and-0, 2-and-1 and 3-and-1 is inexcusable for a reliever with Lugo’s resume. He succeeded in delivering the worst possible outcome.

But there also are bigger factors at work here. The Mets’ bullpen needs upgrading. That’s hardly a secret, and given Sunday’s state of the relief corps, we’re not sure Buck Showalter could have navigated it much differently.

On the surface, staying with Chris Bassitt for the seventh inning after he already was at 97 pitches obviously was a bit of a gamble. Bassitt has exceeded 100 in five starts this season, including a max of 110 on June 3. By those counts, he didn’t figure to have much left after six scoreless innings despite retiring 11 of the previous 13 batters going into the seventh.

On the flip side, Showalter didn’t have Drew Smith standing by — he threw 23 pitches in getting four outs Saturday — and what other option was more reliable than Lugo, who had stranded six of seven inherited runners this season?

Ideally, Showalter gives a clean seventh to a rested reliever. But with a 1-0 lead, he trusted Bassitt to steal him another inning.

Among the list of less-than-optimal choices, that’s what Showalter settled on before getting boxed in when Bassitt gave up a pair of singles and a walk. Did he wait too long for Lugo? Maybe, but Bassitt said he had plenty left for the seventh.

“I wouldn’t have been out there if I didn’t,” he said. “I’ve done that in the past multiple times. Me and Buck have a good relationship that, if I feel good, I’ll go back out. That’ll be a common theme the rest of the year. It’s not a big deal .  .  . If I feel good, I’m not afraid to go 115, 120 kind of thing.”

If Showalter had a healthy Trevor May, this wouldn’t even be a discussion. But for a $280 million Mets team with unlimited resources, the bullpen has become the No. 1 area of need. There’s not really a close second, especially with pitching staffs shrinking to 13 by noon Monday.

The Mets scraped for just enough off Marlins ace Sandy Alcantara to position themselves for the sweep. And for a team that has the National League’s best record, as the Mets (44-24) still do, it has to be better equipped to get those nine outs against the Marlins.

Under Steve Cohen, a superfan owner already anxious for October glory, that’s going to change as the Aug. 2 trade deadline draws closer.

Bottom line, Sunday was just one loss over the course of a long season, and the Mets don’t lose very often. But Flushing can be a greedy place, especially during the good times, and that was the vibe on a picture-perfect Father’s Day afternoon.

Lugo turned out to be the target of that dissatisfaction, the frustration over a missed opportunity. We don’t hear boos much at Citi Field these days, but for some, they’re still only a bad pitch or two away.