It started with an affirming nod of heads between two tough guys at a Santa Monica Gold’s Gym in the summer of 1997. One-time Olympic wrestling contender Mark Kerr was training for his first Ultimate Fighting Championship fight, having dominated in a three-fight, one-night tournament in Brazil two months earlier. Dwayne “Rocky Maivia” Johnson, a former NFL prospect sidelined with a knee injury suffered during his second year with the WWE, approached him.

“Can I take you to lunch?” Johnson asked Kerr, who obliged him at the Firehouse restaurant in Santa Monica. The conversation inevitably drifted to mixed martial arts, as Johnson peppered the 1992 NCAA champion with pointed questions about the unregulated sport. MMA was gaining popularity in Japan, where multiple promotions hired pro wrestlers for “crossover” fights.

“How’s this organization to work for? How’s the pay and do they pay on time? How’s the work schedule? I could tell from what he was asking that he was seriously contemplating his options,” said Kerr, age 29 at the time. “I asked him why he’d leave the WWE, which seemed much more of a stable choice than fighting. When he told me he was losing money on the road, touring 250 days a year for $150,000, I got it.”

The pair exchanged numbers and parted ways, two ships passing in the night. Kerr defected from the UFC to Japan’s Pride Fighting Championships the next year for $200,000-plus paydays, while the babyface “Maivia” returned to the WWE and turned heel, courtesy of Vince McMahon. “The Rock” emerged soon after and the eyebrow-raising Johnson’s career quickly snapped into place.

Between 1997 and 2000, Kerr was the No 1 MMA heavyweight in the world. His record soared to 11-0, but it was a feverish pace no athlete could keep up for long. Kerr was no stranger to drugs; a trainer had turned him onto steroids in his initial fights. Now, Kerr needed relief from the decades of cumulative pain to bolster his endurance for Pride’s grueling 10-minute rounds. Kerr had torn cartilage in his ribcage that pained him with every breath.

“There was never a shortage of doctors [in Arizona] who’d prescribe me opioids,” Kerr said, “and if one said no, I’d just move onto the next.”

Kerr was addicted to Vicodin in a few months, a missed dose creating anxiety, abdominal pain and fatigue. Being no novice to intravenous drugging, popping pills quickly evolved into shooting liquid straight into his veins. Kerr hid his Nubain and morphine bottle in the guest bathroom away from his girlfriend, Dawn. He shot up every morning, sometimes waking hours later slumped over the toilet when he’d dosed too much.

A camera crew captured this period on film, which became 2002 documentary The Smashing Machine. By then, Kerr’s MMA career was over. When he met Johnson a seocnd time in 2003, it was a reversal of fortune. “The Rock”, having been put over by Hulk Hogan at Wrestlemania XVIII the year prior, was a bona fide superstar with two feature films under his belt. Johnson gushed to Kerr about the documentary, as the MMA fighter fretted over his decision to expose his dark underbelly. Kerr hadn’t been offered a fight in over two years. He was no longer an intravenous user, but alcoholism had become Kerr’s daily enemy; he could down four bottles of red wine in one sitting. By the time another Pride offer came around, Kerr was nowhere near fighting shape. On the sport’s biggest stage, he knocked himself out seconds into the contest with of all things, an ill-timed takedown that sent his head driving into the canvas.

Kerr married Dawn and they had a son, Bryce, in 2004. Their marriage remained combustible for years, as Kerr juggled drinking and the odd personal-training job between fights. After his final defeat in 2009, Kerr had no choice but to call it a day. A tarnished former champion was of no use to fight promoters. Kerr pivoted to car salesman, but dreaded getting noticed by potential buyers.

“I could always tell when someone noticed me, even if they didn’t bring it up,” said Kerr. “They always got the same look on their face, as if to say, ‘What happened to you?’”

Meanwhile, in 2009, Johnson landed yet another starring role in Return to Witch Mountain, his 11th film. Soon, Dwayne Johnson, minus “the Rock,” would become a household name.

As Johnson’s trajectory rose over the next decade, Kerr’s took a nosedive. There was job-hopping and three stints in rehab. Dawn divorced him, but their volatile relationship continued as they tried to co-parent their son. Finally, it was the 14-year-old Bryce’s plea that stopped Kerr’s self-destruction in September 2018.

“It was the anniversary of my mother’s death and Bryce said he knew today was a tough day for me, but asked if I could quit drinking the day after,” said Kerr. “How could I not listen?”

Kerr was 10 months sober when Brad Slater, Johnson’s longtime agent, rang about securing the MMA pioneer’s life rights. The call was completely out of the blue. Kerr and Johnson hadn’t spoken in 12 years, and Johnson, the movie star, now had more cache over the roles he chose. Johnson had never forgotten about the Kerr’s documentary and secretly had hoped he’d get to play the tough, yet vulnerable fighter.

Johnson announced the film at a UFC press conference in September 2019. His Seven Bucks Productions would be at the ship’s helm, with writer-director Benny Safdie its rudder. Safdie set to work adapting the documentary into a screenplay, mining Kerr for additional scenes to flesh out Mark and Dawn’s relationship.

“When the pandemic hit in March 2020, I thought it was over for the film,” said Kerr, who’d resigned himself to a quiet Arizona life. “If it was meant to be, it would all fall into place.”

In sobriety, Kerr reconnected with a gym friend named Franci. They began dating during the pandemic and would marry on New Year’s Eve 2023.

During the pandemic, Kerr didn’t hear a peep from Johnson, Safdie or Seven Bucks, but sometime during the 57-day shoot for Oppenheimer, Safdie convinced co-star Emily Blunt to watch the documentary. Blunt, a longtime friend of Johnson’s, immediately called her Jungle Cruise co-star, telling him the time was now to get the film done. Blunt signed on to play Kerr’s girlfriend, Dawn, and the fire was lit.

Kerr received another call from Slater in September 2023, but this time there was a starting date that spring. Kerr toured the Vancouver film set that April and filming began that May. Per Johnson’s request, Kerr didn’t visit the set during shooting.

“DJ had never played a living person before and I respected that process,” said Kerr. “I’m glad I stayed away. When my son saw the film, he couldn’t believe how DJ got down my [softer] speech and mannerisms. My own son!”

Indeed, Johnson’s turn as Kerr is convincing, especially for those that know the retired fighter. Johnson received a 16-minute standing ovation for the film at the Venice Film Festival, while the innovative Safdie took home its distinguished director’s prize.

For the 56-year-old Kerr, it’s a second chance at notoriety, however fleeting that might be. Johnson has been adamant that Kerr be at his side for most of the film’s promotional tour.

“It’s amazing that a small decision I made decades ago, to keep the [documentary] cameras rolling while my life crashed and burned, grew into all this,” said Kerr, who plans to write a book next. “I couldn’t be happier with how this all turned out and I can honestly say that I’ve gained friends for life from it.”