The walls were once closing in on Erin Henderson. But now, he’s finally free.

“Free as a bird,” he said with a smile, during a recent interview with Newsday.

There was a time not too long ago when Henderson’s football life and his freedom were at risk; a time when so much uncertainty, so much unhappiness clouded his entire world. But after six seasons in Minnesota, and a year away from football, the Jets inside linebacker has found inner peace, a new team and a starting job in Florham Park, New Jersey.

“You come in here and the windows and all that light and that sunshine,” Henderson said, referring to the Jets’ spacious, state-of-the-art facility. “The people around here, the people that you work with and deal with — when you come into this locker room it’s a night-and-day difference. I’m able to be myself here. I don’t have to hide anything here, I don’t have to pretend to be somebody I’m not.”

He doesn’t shy away from his past, nor does he sugarcoat the depths of the darkness that used to envelope him.

On New Year’s Day 2014, Henderson found himself in a jail cell — his punishment for his second suspicion of driving while intoxicated arrest in a six-week span, according to the Carver County Sheriff’s Office in Chaska, Minnesota. He was also found possessing drug paraphernalia and 1.4 grams of marijuana, according to the police incident report. But he refuses to be defined by his past transgressions. Instead, he’s focused on making the most of his second chance.

He signed a one-year deal for the veteran minimum during the 2015 offseason to be a backup and special-teamer with the Jets. But by season end, he had impressed the organization enough to earn himself a two-year, $3.1-million deal in March — “the biggest contract of my life,” the 29-year-old said, proudly.

And now, there’s no containing his joy — or his voice.

Chatterbox

Henderson is chirpy, full of energy, and eager to have the last word on the field. No one is safe from his playful barbs, not even veterans such as Brandon Marshall or young quarterbacks Bryce Petty and Christian Hackenberg.

“Erin’s always been a talker behind the scenes,” coach Todd Bowles said. “But lately he’s become more of a, shall I say, vocal leader in that regard . . . If you know him, it’s all in fun. He gets the guys going and he likes to cause little stir-ups out there every now and then. But it was good camaraderie.”

Henderson has much to be happy about now. He was a long shot to make the team when he first arrived, but by November he was sharing time with Demario Davis. Now, Davis is in Cleveland and Henderson has his job, teaming with veteran inside linebacker David Harris.

“I like to talk,” Henderson said of his chatty ways. “It helps me out, it helps my teammates out. It keeps everybody going. It’s a reminder that every down is important, every play is important.”

And no one understands that better than Henderson.

While with the Vikings, he was arrested on the afternoon of Jan. 1, 2014, after he lost control of his SUV and crashed into trees in a parking lot. Henderson — who had also been arrested on Nov. 19, 2013, “for probable cause DWI and possession of a controlled substance,” according to the Eden Prairie, Minnesota, police department — said he asked to be kept in jail for two days following his second transgression.

“‘Get yourself together. This is your warning,’” he remembers telling himself while alone in his cell. “For me to walk away from that car accident unscathed, without a scratch. My car was completely totaled. That was my wake-up call. Somebody was watching out for me. Somebody was looking over me. But somebody also wanted me to get myself together.”

Free spirit

From jail, he went straight to rehab, Henderson said. And he refuses to slip up again.

“I understand the importance of my job, my actions, and the ramifications that go along with it,” he said. “I don’t really have a lot of room for error. I don’t have the gray area that a lot of people have and the chances a lot of people have.

“I’ve already wasted mine.”

But Henderson is more than just a cautionary tale. He’s a man who embraces his shortcomings, but refuses to be defined by them. And he’s on a journey to prove the Jets made a wise choice in re-signing him, even though he turns 30 on July 1.

When he signed, he was honest with members of the Jets’ front office. “There’s nothing glamorous about me, nothing fancy,” Henderson remembers telling them. “I’m not going to go out and have a great workout, you’re not going to love my 40 [-yard dash] time, but I can play the game of football. And I’m going to come out here and I’m going to give y’all my all, especially if y’all are giving me an opportunity when a lot of people are closing doors on me.”

No longer is he trying to “escape” the problems that once plagued him. Now, he’s simply enjoying the fresh air and the fresh start he’s found in Florham Park — a place where the walls never feel like they’re closing in on him.

“Nah,” Henderson said with a smile, as he stretched his arms out wide in the locker room. “How could they be?”