NEW YORK -- These days, few situations vex the Mets more than holding a late, slim lead on a night that Seth Lugo is unavailable to pitch. For all intents and purposes, Lugo has become New York’s closer. But the Mets often use him for multiple innings at a time, indisposing him for at least one day after each appearance.

So it was Tuesday, when the Lugo-less Mets found themselves on the receiving end of a strong Zack Wheeler start and a three-RBI game by Todd Frazier, with six outs to go. Then five, then four, though that’s glossing over the details. At some point, a fatigued Justin Wilson found himself searching for one last out to lock down a four-out save.

Wilmer Flores stepped to the plate.

“Of course it had to be him,” Frazier said.

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On this night, however, the Mets’ bullpen did not break. With Lugo watching from the Citi Field bullpen out of necessity, and Edwin Diaz doing likewise due to “a very difficult” managerial decision, Wilson struck out Flores to end the Mets’ 3-2 win over the D-backs.

“Interesting ninth, for sure,” Wilson said. “Interesting eighth, too.”

With the Cubs losing to the Padres on Tuesday night, the Mets now sit three games behind Chicago for the second Wild Card spot, though there are three teams between them (D-backs, Phillies, Brewers). The Phillies and Brewers both won on Tuesday, and Milwaukee now sits a game behind Chicago, though the Brewers lost their best player -- 2018 NL MVP Christian Yelich -- for the season after he suffered a broken right knee cap when he fouled a ball off of it.

This was hardly the way the Mets drew things up when they constructed their bullpen mostly from scratch this winter. To pitch the ninth, the Mets invested significant prospect capital to acquire Diaz, arguably baseball’s best closer last season. To pitch the eighth and sub at closer on occasion, the Mets signed Jeurys Familia.

Neither of those pitchers proved trustworthy over the season’s first five and a half months and the Mets, needing to be near-perfect over the remaining three weeks if they are to score a playoff berth, are well past the time for gambling on a rebound. Last month, they installed Lugo as their closer in most situations, but Lugo -- a multi-inning weapon pitching with a partially torn UCL in his right elbow -- is never available the night after recording six outs in a game.

He achieved precisely that on Monday, mowing down six D-backs to preserve a Mets win. So Tuesday, the Mets came into the night hoping Wheeler could pitch into the later innings, and some other reliever could do the rest.

Wheeler completed his mission, recovering from a rocky first to scatter seven runs over seven innings, and Frazier provided the offense with a two-run double in the second inning and a one-run double in the fourth. When the eighth inning arrived, Mets manager Mickey Callaway turned first to Brad Brach, who allowed a one-out homer to Eduardo Escobar, thinning the Mets’ lead to a single run.

Next up was Wilson, who entered the game intent on finishing it.

“Late in the season, everything kind of goes,” Wilson said. “We’ve got to win games.”

For Wilson, who battled command issues, the ninth inning was not formulaic. Singles by two of the first three batters brought up Ketel Marte, who bounced a ball to first base. Watching it come off Marte’s bat, Frazier hoped Pete Alonso would tag the trail runner and tap first base, ending the game. Instead, Alonso “spazzed out there a little bit,” in Frazier’s words, ignoring the runner and tagging first. The Mets recorded only one out, bringing Flores to the plate with the potential winning run on base.

Over six years in Flushing, Flores accumulated more walk-off RBIs than any Met in history. Wilson, who was unaware of that history, mowed him down all the same.

“It is difficult,” Callaway said. “He didn’t have his best stuff. He didn’t have his best command. He’s going to need a day or two off, but it’s worth it for the win tonight. He was unbelievable. He just kind of willed that game, that save, and that’s what you have to do.”

The win confirmed the Mets are done following any set bullpen formula. Although Flores was a significantly better matchup on paper for Diaz, Callaway stuck with Wilson to avoid putting his embattled former closer in that situation. The result was a success.

“I just had to,” Callaway said. “We all know the struggles Diaz has had, and Wilson has been really good. … He willed it. I’m not saying we’re going to run from Diaz. He’s going to get his chances, too. But tonight, we called down there in the eighth and asked Wilson if he could get four outs for us, and he did.”