For years, Rashard Mendenhall felt constricted, typecast as a character that didn't embody who he truly was. Something was missing in what seemed like an otherwise perfect life as an NFL running back.

But in his football retirement, he has discovered a more creative, fulfilling way to connect with a game he still loves.

Barely 19 months after his final carry, the former Steeler works as a staff writer for "Ballers," a new HBO series about a pro football player turned financial adviser (played by Dwayne "The Rock" Johnson) who helps NFL players traverse everything that comes away from the field.

Away from football, he has found a calling.

"It's something that I hadn't envisioned, but it's been more perfect than anything I could have envisioned," Mendenhall said.

On a show depicting a side of pro football few get to see, Mendenhall's voice has been a salient one. Though producers consulted a number of former and current players during the series' development, only Mendenhall and Baltimore Ravens linebacker Terrell Suggs ever read a script.

Mendenhall not only proofreads material for its authenticity — from how players talk to what they do in the offseason — but he also works with the show's writers in developing stories and characters.

"He was very valuable in the writers' room," said Evan Reilly, one of the show's executive producers. "He was a surprisingly fast learner in an environment that — if you've never been in a writers' room before — can be very noisy and competitive. We wondered if maybe he'd be out of his depth, but he hung right in there."

Walking away from the game: At an age when, even for a running back, he was entering his physical prime, Mendenhall walked away from a lucrative, highly visible and largely successful career in March 2014 to chase other passions like reading, writing and traveling.

He never fell out of love with football; rather, many of the things that were saddled with it became onerous.

Life in the NFL was all-consuming, so much so that Mendenhall said he constantly felt like he was in a box. When he would do something as simple as post a picture of a book he was reading on social media, he would be hounded by people asking him why he wasn't reading a playbook.

What was once a beautiful opportunity devolved into a burden.

"In the eyes of people outside of it, you can never really be apart from it," Mendenhall said of pro football. "You can never be yourself; you have to be [a pro football player] at all times. That's a heavy task to endure."

Liberating retirement: Retirement was, in many ways, liberating. In a first-person essay he penned for The Huffington Post announcing his retirement a year and a half ago, Mendenhall wrote that he planned "to live in a way I never have before."

His words caught the eye of Reilly, who shared the piece with "Ballers" creator Stephen Levinson. For a show that delves behind the facade of the NFL, Mendenhall was a perfect fit, someone who had a different perspective on pro football without harboring a vendetta against it.

Through insight and hard work, Mendenhall turned what was originally arranged as a monthlong tryout into a full-time job and, perhaps, a new career as a screenwriter.

"He's the kind of guy who feels like, to me, whatever he puts his mind to, he's going to do," Reilly said. "He's got a lot of confidence without being cocky, and he's willing to put in the work. A little bit of talent helps, and I've seen that thus far.

"I really feel like he's got it,and it's just going to take a little time."

Finding peace and joy outside the NFL: That work, at least for now, will continue. Earlier this month, HBO renewed "Ballers" for a second season, and Mendenhall, who lives in Santa Monica, Calif., has been working with Reilly and others to piece together new storylines.

When the NFL season kicks off in September, Mendenhall will be far removed from the stage that for so long defined who he was to the outside world. But away from that, he has found a new kind of peace and joy.

"I look to continue to grow and evolve as I learn through 'Ballers' and as I put my own interests and own ideas out there to tell stories," he said. "This is just the beginning for me."