PORT ST. LUCIE — The epicenter of the Mets clubhouse is a row of five lockers along the far right side.

They belong to — left to right — Matt Harvey, Noah Syndergaard, Jacob deGrom, Steven Matz and Zack Wheeler, and whether it is pre-workout or pregame, there is a gravitational force that draws all comers to the area. About an hour before Monday’s game against the Nationals, for example, deGrom, Harvey, Jerry Blevins, Travis d’Arnaud and David Wright ate lunch in a clutch of chairs around the lockers with Jeff Wilpon joining in.

This is Broadway in the Mets clubhouse, the non-Cespedes reason for championship optimism.

Beyond Wheeler’s corner locker is the path to the training room and then the opening to the shower/bathroom area, and then another strip of lockers go up the far wall at a right angle. The first two belong to Robert Gsellman and Seth Lugo. This begins off-Broadway.

“We are blessed with two pretty good off-Broadway stars there,” assistant GM John Ricco said.

Gsellman and Lugo understudied their way into prominence last year, from invisible to invaluable.

“We wouldn’t have made the playoffs without those two guys,” Mets bench coach Dick Scott said.

In a combined 15 starts, they were 8-3 with a 2.66 ERA, helping the Mets survive the late-season absence of every member of Broadway except Syndergaard.

There is pretty much no doubt the Mets will need the duo as much this year since that celebrity row is mostly held together by hopes, prayer and surgical scars — all but Syndergaard a Tommy John survivor already and having not pitched a major league game since their most recent procedure.

The five members of Broadway — despite their renown as a group — have never gone a turn through a rotation together. Not one. And the likelihood is Matz will begin the season on the DL, his most recent injury (elbow tenderness) raising exasperation from a front office that wonders if he will ever stay serially healthy.

Gsellman said no one has told him he is in the rotation, but it seems like he has crossed that velvet rope. In which case — should Matz be out — the No. 5 spot will go to Lugo or Wheeler. If that decision were based exclusively on their duel at 40 miles Monday — Wheeler excelling (five shutout innings) in Jupiter against the Marlins, Lugo sagging (4 ¹/₃ innings, four runs, three homers) at home against the Nationals — then Wheeler will be the man.

[mlbvideo id=”1249984383″ width=”600″ height=”340″ /]

However, the Mets have to weigh Lugo’s strong effort last season in a pennant race and as the ace for WBC runner-up Puerto Rico against Wheeler’s higher ceiling, but also large questions surrounding whether he can be consistently sharp and healthy, and when exactly is the best time for the Mets to exhaust the roughly 120 innings they will let him throw after missing two seasons?

“If [Lugo and Gsellman] don’t start the season, we’re going to turn to those guys [at some point], and we feel real comfortable with them,” Terry Collins said.

That Lugo and Gsellman get entangled as a subject is a matter of the timing of their promotions, but not reality, Mets people say. Gsellman, they insist, was always on their radar. Scott [who used to run the minor league operations] said internal reports from a similar point of development had Gsellman ahead of deGrom, the patron saint for coming from nowhere to get to Broadway.

In Gsellman, the Mets saw the possibility of his sinking fastball, athleticism, competitiveness and poise and, yes, it played up a bit in the majors, and now Collins talks about the righty’s overall stuff as if discussing one of his Broadway stars.

Lugo was a 34th-round pick, yet intrigued the Mets because he seemed to have an instinct to pitch. But they saw him more as a swing type, at best. Since he had failed at Triple-A, no executive saw his late-season contribution coming.

[mlbvideo id=”1245446483″ width=”400″ height=”224″ /]

That is why there is more hesitation about Lugo, who said after pitching in three playoff-like atmospheres in the WBC, including the title game versus the U.S., that it was difficult to create the same adrenaline Monday. Scott, who was the acting manager at home, said he understood, but twice pointed out that the Nationals brought their “A” lineup (minus Daniel Murphy) and that plus the competition against Wheeler “was incentive enough to perform.”

Lugo said he was not pitching with an eye on Wheeler. But Wheeler said he was trying to win a competition. He did so with Collins, pitching coach Dan Warthen, Sandy Alderson and Ricco watching, which befitted his mysterious status, but also his spot on Broadway.

”Wheeler is the linchpin of a lot of our discussions,” Ricco said. “We can get caught up in Opening Day, but the reality is he is real close. And the reality also is you start with five, but if you are lucky you only need eight [starters] all year. We feel good about seven.”

This where Broadway — on and off — merge. The Mets know they are going to need the whole cast before the curtain drops.