Seth Lugo of the New York Mets pitches in the...

Seth Lugo of the New York Mets pitches in the first inning against the Washington Nationals at Citi Field on Sunday, Sept. 4, 2016. Credit: Jim McIsaac

If the Mets finish this improbable rally for the second wild card by riding the arms of Seth Lugo, Robert Gsellman and Rafael Montero, winning Manager of the Year won’t be enough for Terry Collins.

We’re thinking Nobel Prize.

Because after navigating the Mets through the nearly total breakdown of their starting rotation, maybe Collins can spend the offseason tackling something less challenging, such as developing a Zika vaccine or slowing climate change.

Simply put, what’s happening right now for the Mets shouldn’t be happening. It defies any plausible explanation. One by one, they gradually have lost the rotation core that propelled them to the World Series, and they still have almost completely erased a 5 1⁄2-game deficit in two weeks.

On Sunday night, Lugo needed 47 pitches to survive the first two innings, yet stuck around for seven in leading the Mets to a 5-1 victory and a series win over the Nationals. He allowed only Danny Espinosa’s second-deck solo homer in improving to 3-1 with a 2.19 ERA in four starts as the sub for Steven Matz. When finished, he walked off to a standing ovation. “That was pretty awesome,” he said.

We used to view Lugo and Gsellman, a pair of lower-round 2011 picks, as temporary placeholders, Vegas guys keeping the rotation spots warm for Matz and Jacob deGrom. Not anymore. There’s no guarantee we’ll see either one again this season, and judging by the pace of their rehab stints, don’t get your hopes up.

Matz, who is nursing a rotator cuff impingement, hadn’t picked up a baseball before flying to Port St. Lucie this weekend. There’s no telling when his shoulder will feel sturdy enough for him to contribute again. And it’s not as if the bone spur in his elbow has vanished.

As for deGrom, the more we hear about his forearm soreness, the worse it sounds. The Mets had said he’d miss his next start, but Collins suggested Sunday that he might need to skip two turns, minimum.

At this point, it’s all just educated guesswork. DeGrom hasn’t been himself for almost a month now (0-3, 9.82 ERA), and the extra time off didn’t appear to dent what was bothering him.

When Collins was asked Sunday about him, he replied, “He’s resting right now.” That’s the kind of response you get when your grandfather can’t come to the phone.

Bottom line, neither Matz nor deGrom will be ready to throw a pitch for the Mets anytime soon. If you had presented this scenario at the All-Star break, we’d have stuck a fork in the club. Three-fifths of the rotation toast and still in contention? No shot. But they are.

The Mets have used 10 starting pitchers this season — same as a year ago — but their rotation meshed toward the end in 2015 rather than coming apart, as it has this year. Collins and Co. knew what to expect because they were the organization’s elite arms, and that group lived up to the hype.

What was there to know about Gsellman, other than his reliable sinker and deGrom-style flow? Or Lugo, whose gravity-defying spin rate for his curveball made him a StatCast darling but couldn’t prevent a 6.50 ERA at Triple-A Vegas?

The Mets dealt eight minor-league pitchers before last year’s trade deadline, including two of the best — Michael Fulmer and Luis Cessa — in acquiring Yoenis Cespedes.

Suffice to say, Fulmer (10-6, 2.96), who is lined up for serious Rookie of the Year consideration, would be a big help now, and Cessa (4-0, 4.17) is in the Yankees’ rotation. Instead, the Mets are hoping Lugo and Gsellman can be saviors, with Montero — the fallen prospect — using the No. 5 spot in an effort to redeem himself.

“We made so many trades last year, you weren’t sure what was left,” Collins said. “We’ve asked them to step up, and they’ve stepped up.”

That’s got to continue for the Mets to make it back to the postseason. And we’re becoming less skeptical by the day.

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