NFL

A hyperbaric chamber, magic tricks, holistic diet: life as Rashad Jennings

Before every game, Rashad Jennings cannot contain himself as he shouts to his teammates, “Don’t let anybody define you!’’

Words from the heart from a player who has been sidestepping and vaulting definitions placed upon him for quite some time.

“I was defined when I first came in as a third-string back, a third-down back. Then I started playing well on special teams — he’s a special teams guy,’’ Jennings said in an extensive interview with The Post. “Then I was bigger, I was defined as a bruiser. You make a long run, hmm, then you start pass protecting, hmm. They’re always trying to put labels on you.

“For me, my label is the only one that matters, and that’s striving to become a complete back. I refuse to let anybody define me.’’

In his mind, Jennings was never a backup, never an understudy. But the game was not played in the mind of Rashad Jennings, so what he experiences Monday night in Detroit will be new to him.

Never before has an NFL team at the start of a season opened the door to its running game and told Jennings, “Come on in, we need you.’’ He will make his Giants debut, start at running back and, at 29 years old, will open a new chapter of his professional life.

“I’ve had to overcome a lot of giants in my life to actually become a Giant,’’ he said, completing a perfect sound bite.

No real games have been played, but thus far Jennings’ arrival easily can be characterized as a “seamless transition.’’ The Giants are banking on him to be a durable, dependable runner, a reliable pass-catcher out of the backfield and a protector of Eli Manning in blitz pickup — everything they did not get from their running backs last season.

Jennings is banking on doing it all.

“Being now in New York, it’s a kid in Toys R Us,’’ he said.

Rashad Jennings celebrates a preseason touchdown.Paul J. Bereswill

His interview sessions are more like motivational gatherings, and it hard to believe he is such a newcomer to the Giants locker room, given how naturally he already fits in. As a seventh-round draft pick from Liberty, sticking around on an NFL roster was a big deal. He served as backup to Maurice Jones-Drew for four years in Jacksonville, and last year behind Darren McFadden with the Raiders. The Giants last season were an absolute mess in the backfield, sorting through nine runners in an injury-filled and production-starved season that ranked them 29th in the league in rushing.

When free agency hit, the Giants called Jennings in the first few minutes, and it wasn’t long before a four-year, $14 million deal was finalized. So far, he has been everything the Giants hoped and wished for, and his performance, along with rookie Andre Williams, was the crack of light in what was a dark summer for the offense.

“We’re not looking back there wondering who’s there and wondering what’s going on back there,’’ receiver Victor Cruz said. “It gives us stability, it gives us a renewed sense of confidence that we are blocking for a guy that’s going to be there, blocking for a guy that’s a special running back, he’s a really good player, too, so it helps in that regard.

“It just flowed, man. Rashad’s one of those guys that, he gets it, he understands exactly what’s asked of him. I’m excited for him.

“It’s his time. Every athlete gets his moment where he either grasps it and gets it or it falls by the wayside, and I think this is his moment and I think he’ll make the most of it.’’

One look at Jennings is all it takes to figure out his deal on the field. He’s 6-foot-1 and 231 pounds with a linebacker-type torso and arms that look as if they could squeeze the air out of a football. He has averaged 4.3 yards in his 387 NFL rushing attempts and was fast enough to outrun everyone on a 73-yard touchdown sprint in the preseason against the Steelers.

The Giants did not import a star but, more likely, a steady professional who will grind it out for them. Someone who is so in tune with his physical aura that Williams, his backfield mate, marvels, “His warmup lasts probably until the middle of practice, making sure his body is primed and ready to go.’’

Just as corralling Jennings on the field is a rough assignment, putting him in a box off it is unwise — unless it is a very large box. Rarely does he engage in something the way others do.

He either sleeps or takes a nap in a hyperbaric chamber every day. His eating habits are so disciplined he won’t even take a nibble of anything served in the Giants’ cafeteria — which has gone almost completely organic — even though he admits, “It’s good food.’’ Instead, he has a chef prepare his meals, which are packaged and dropped off at the team facility.

Eli Manning hands off to Rashad Jennings.Getty Images

“I do not like playing Russian roulette in the kitchen,’’ Jennings said. “I like to know what I’m gonna have, how much I’m gonna have.’’

Jennings describes his diet as gluten- and casein-free and everything “as organic as possible, as holistic as possible.’’ He makes and drinks the same breakfast shake nearly every morning, a 12-ingredient storehouse of nutrition that includes nice helpings of Hemp seed and flax seed oil. Cocoa Puffs it is not.

Teammates may look at him as either a mad scientist or something of a kitchen crackpot.

“The guys laugh and joke on me,’’ said Jennings, who slowly has made a few converts.

Cruz one morning wandered over during the breakfast shake assembly and said, “Man, let me taste that.’’ The next day, it was, “You got any more?’’ The next day it was, “Hey Rashad, can you make me one?’’ Perhaps before long — especially if Jennings runs for 100 yards in the season opener — there might be a line formed to get a sip.

Everyone has some sort of weakness or vice, but Jennings’ sounds as if he has processed all the fun out of his. He says he loves chocolate chip cookies and muffins. He takes those favorites and puts them in a juicer, collects the pulp and adds in gluten-free flower and maybe some vegan chocolate to form a muffin.

“It’s so good for you and it’s so good period,’’ Jennings said.

He is right-handed but taught himself to also write with his left hand. He once was unhappy as a kid with a scribbled autograph he received, then promised himself if he ever got famous he would sign in penmanship fans would appreciate. He takes painstaking time when he signs, using spiraling circular flourishes, with the finished product almost looking like musical notes.

He plays guitar and already has delighted and confounded his new teammates with magic tricks and sleight-of-hand moves. Out of nowhere, little red balls appear in your pocket when you’re around Jennings. He especially enjoys doing card tricks on the hulking linemen who, Jennings says, have “the big-guy syndrome, they don’t like to get tricked.’’

There is not much he hasn’t done or wants to try. He has worked to prevent juvenile asthma, rescued abused animals and after each season rounds up 40 kids from a poor community and takes them to his alma mater, Liberty College, for a weekend program designed so show the kids the possibilities that arise from education.

Jennings stretches out during training camp.Paul J. Bereswill

Jennings, who is from Lynchburg, Va., spent only one season with the Raiders, but he used his time on the West Coast to tour Silicon Valley, “exploring and taking the opportunity to network and shake hands’’ with executives at headquarters for Facebook, Twitter, Google, Pixar and WellnesFX. It’s all part of a plan to expand his base.

“Curiosity outperforms formal education to me,’’ he said.

And now, he is in New York and he already has noticed more people are interested in who he is, on the field and off it. He knows the opportunities here will be bigger than anywhere else he might have been.

“To say anything else would say my awareness is at zero,’’ Jennings said. “Still, for me, my focus is … to look in that little kids eyes in myself and tell him ‘I have his back.’ ”

Jennings said he is sure he will shed more than a few tears Monday night as the national anthem is played.

“I know I have a lot bottled, but the level of excitement will probably show on my face,’’ he said. “It’s a start to a new season, earning trust by the coaching staff, teammates to be the first out there at the position means a lot. To be in this organization doing it, under the lights on Monday night you can’t get any higher than that. It’s humbling.’’