The helicopter banks 45 degrees over the Hudson River, gliding toward the West Side of Manhattan.

Its landing spot — a white circular outline at the edge of the West 30th Street Heliport, practically at the water’s edge — quickly comes into view.

The rotor blades slice through the air, creating a cacophony of sound as Jets teammates Brandon Marshall and Eric Decker, who’s happy to catch a ride into the city, disembark. Thank yous are exchanged with the pilot before Marshall sets off on the second leg of his trip just hours after the first day of Jets mandatory minicamp.

Tuesday’s 15-minute helicopter ride from Morristown Airport in New Jersey to New York City is followed by a chauffeured drive to his doctor’s office in Midtown. Hours later, Marshall and Decker are back in the SUV with tinted windows for the return commute through the Lincoln Tunnel, during rush-hour traffic, back to New Jersey.

These are the lengths Marshall, 32, will travel to attempt to reverse the wear and tear on his body from more than decade in the NFL.

The star receiver is precise with his workout regimen, nutrition and sleep schedule.

Over the course of three hours late Tuesday afternoon, Marshall provided rare access to his world. And as the day went on, he and Decker offered a window into their friendship and also sounded off on NFL contracts, minimum salaries and the shrewd negotiating practices of teams.

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After FaceTiming with his twins on his laptop and conducting a half-hour video conference for his foundation in the locker room (“I would never do that during the season,” Marshall insists), he heads out to practice under the blazing sun. But even after team drills, treatment and meetings have ended, Marshall’s day is far from over.

5:40 p.m.

Morristown Airport

Decker’s silver Range Rover turns into the parking lot at Hangar 1 at the end of Airport Road. Marshall, dressed in a casual all-black ensemble, hops out of the passenger seat.

They’re running late.

The helicopter, conveniently located five minutes from the Jets’ Florham Park facility, was scheduled to depart at 5:30 p.m. The pilot greets Marshall and Decker, who’s wearing a T-shirt, shorts, flip-flops and a hat turned backward, before escorting them through the passenger terminal and outside toward the chopper.

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5:44 p.m.

Somewhere over New Jersey

A sea of lush greenery stretches for miles below, with parking lots, baseball diamonds and football fields interspersed. Soon, crowded highway lanes come into focus.

“Look at all the traffic we’re avoiding,” Marshall says through his headset, pointing from the front seat.

As the helicopter makes it way across the Hudson River, the New Jersey coastline gives way to a breathtaking panorama of lower Manhattan. Decker, seated behind the pilot on the right side of the chopper, has an unobstructed view of the Statue of Liberty and the Freedom Tower in the distance.

Gliding over a cluster of recreational boats, the pilot begins to ease the aircraft at an angle toward the West 30th Street Heliport. Soon, Marshall and Decker are greeted on the ground by Pat Day from Liberty Helicopters, which, through its partnership with Blade, offers Uber-like airfare service. The Jets receivers then jump into a black Ford Explorer. The driver weaves his way through stop-and-go crosstown traffic toward the intersection of East 48th Street and Madison Avenue.

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6:18 p.m.

Midtown Manhattan

The elevator doors open into the waiting area of Suite 901 — the office of NY Spine Medicine.

Two turquoise ottomans in front of the receptionist’s desk provide a pop of color against the backdrop of gray walls and black, white and gray leather seats. After a few minutes, Dr. Edward Capla escorts Marshall down a narrow hallway and into a small exam room.

“Brandon’s like my new spokesperson,” Capla, the Director of Molecular Cell Orthopaedics, says with a smile.

He explains the benefits of the Regenokine Program, which halts the progression of inflammation in the body, thereby allowing “good cells” to penetrate and allow healing to take place in arthritic joints.

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“It’s what a lot of people call ‘the Kobe Bryant shots,’ ” Marshall says. “For older athletes . . . this is like the fountain of youth.”

Marshall said he usually gets multiple injections right before training camp or “on an as-needed-basis, like last year. I had two turf toes and I had a knee thing going on.”

After the Jets’ loss in Oakland last Nov. 1, Marshall went to see Capla. “So, I was able to kind of recover fast and not miss any games.”

He also had a breakout year in his first season with the Jets. He caught a career-high 14 touchdowns, set a single-season franchise record for receiving yards (1,502), had 10 games of 100-plus receiving yards to surpass Don Maynard’s 1967 team record, tied Maynard and Art Powell for the most touchdown catches in a season, and also earned his sixth Pro Bowl selection.

“When you get older, when you start seeing those guys fall off, it’s because their joints are so unhealthy,” says Marshall, who’s about to receive injections in both knees and big toes.

According to Capla, anti-inflammatory proteins produced naturally in the body are first extracted from a vein in a patient’s arm and then a selection of recombinant proteins from the blood are isolated and placed in an incubator. The blood is heated over the course of “20 to 22 hours” to create a serum customized for each patient, their symptoms and specifically-targeted areas of the body. The serum, which consists of “140 times” the amount of “good proteins” is then injected into the arthritic joints.

“So, the serum in his toe, we can’t use it for his knee,” Capla adds. “Everything has a protocol to it and it’s all derived through mathematical algorithms and specific concentrations.”

It entails a series of five injections in each body area, depending on which joints need treating. It’s all natural, all legal, Marshall and Capla point out.

It isn’t easy for NFL players — particularly veterans — to commit the time, energy and money that Marshall puts into his regimen. He said he spends around $200,000 annually on mind and body maintenance, including nutrition, massages, MAT (muscle activation techniques), dry needling, talk therapy and meditation.

“You have to do more, and that can be exhausting and overwhelming at times,” says Marshall, who was traded from the Bears to the Jets in March 2015. “Some guys, that’s where they lose. It’s not that they can’t do it anymore, but they don’t want to go through the process.”

7:49 p.m.

Lincoln Tunnel

The SUV has snaked its way through crosstown traffic, bypassed an accident involving a compact car and a taxi and successfully avoided a near-accident between two vehicles just before the entrance to the Lincoln Tunnel.

Decker, who came to the Jets from the Broncos in 2014, is in the front passenger seat, his face buried in his iPhone. So is Marshall, who’s seated directly behind him. But it’s not long before they both erupt in laughter and trade playful barbs.

“Today he told me, ‘I honestly thought you were a product of Peyton [Manning]. Like I didn’t believe you were good,’ ” Decker says.

Marshall lets out a giggle, demonstrating his guilt. “I did,” he says, smiling. “[I used to think] ‘Man, it’s not fair, they have Peyton,” reinforcing the idea that the success of Denver’s receivers are “a product of Peyton.”

He had been a fan of Decker’s game in college, but Marshall had assumed the former Bronco’s eye-catching stats — 172 receptions, 24 touchdowns and 2,352 receiving yards combined in 2012 and 2013 — were an indication of luck, rather than talent. But he began to see Decker in a new light last year.

“He’s probably one of the better route runners in our league,” Marshall says of his buddy. “And I don’t think people really understand it — I didn’t even really . . . And then, probably during the Indy game [in Week 2], I was like, ‘Wow, this dude is pretty good.’ ” Decker caught eight passes for 97 yards in the Jets’ 20-7 win.

Together, Marshall and Decker combined for 26 of Ryan Fitzpatrick’s franchise-record 31 touchdowns last season. And they’re hoping the bearded quarterback re-signs so they can build off last year’s 10-6 record. But like their coach Todd Bowles, they’ve grown tired of talking about it. “It was funny and cool at the beginning,” Marshall says of the Fitz fodder, “Like, you can throw some punchlines in there. But now it’s like, it’s time to roll.”

Jokes eventually give way to a serious discussion about the NFL. Marshall and Decker view the system that generates exorbitant profits for billionaire owners as hypocritical, ignoring the financial stability of all of its players.

Days before Jets defensive end Muhammad Wilkerson publicly voiced frustration over his contract negotiations and Marshall tweeted “It’s time to liquidate the Franchise Tag,” the Jets’ biggest offensive stars were sounding off on league salaries and negotiations together.

“I feel that once you’ve outplayed your contract, you should be back at the table,” Marshall says. “And I think it should be an open discussion, and a fair discussion, and an expected discussion . . . A guy signs a five-year, $50 million contract with $20 million guaranteed. So let’s say the first two years are guaranteed, pretty much. So, say year two, you don’t produce at that $10-million level, what are teams doing? They say, ‘Hey, we need you to take this pay cut or else we’re going to cut you.’ And they’re also using this tactic of waiting until the last minute to cut you when the free-agent market has (dried up).”

Some may question why Decker — who signed a five-year, $36.25 million deal with the Jets in 2014 — and Marshall — who made $9 million last year — would question the motivations of owners. But they say they’re advocating on behalf of all players, not just themselves. Says Marshall: “We’re just looking at pure, just business, and the numbers that professional athletes and owners work with.”

He thinks the NFL minimum salary should be $1 million. (Currently, the minimum wage-scale starts at $450,000 for players with less than a year and maxes out at $985,000 for players with 10 or more years in the league.)

Marshall and Decker strongly believe the NFL should take better financial care of practice-squad players too. They “deserve a heck of a lot,” says Marshall, “These guys’ bodies are probably more beat up than anybody on the field.” In 2015, practice-squadders made no less than $6,600 a week, but less than players on the active roster.

“Obviously, we’re the product of the NFL and TV has changed the scope of football,” Decker says . . . It’s the players who are the ones who drive the NFL, so compensation — because you’re not going to be in this game for a long time — is the No. 1 thing. Guys need to be taken care of while they have the opportunity.”

8:25 p.m.

Morristown Airport

Just before the sun sets, the Ford Explorer pulls into the parking lot at Hangar 1.

The teammates exit the vehicle and prepare to go their separate ways. Marshall retrieves his bag from Decker’s parked Range Rover, then climbs back into the black SUV.

Tuesday’s odyssey is complete. But the next day, Marshall plans to do it all again: practice, followed by another trek to Manhattan for “Kobe” shots.