LAS VEGAS — As Jon Jones, one of the greatest athletes in the history of the Ultimate Fighting Championship, walked toward the octagon for his heavyweight debut after a three-year hiatus from the sport, the red lights dimmed at T-Mobile Arena. The crowd, which included the retired N.F.L. quarterback Tom Brady, the actor Mark Wahlberg and the mixed martial artist Conor McGregor, roared.
Francis Ngannou, 36, would have been an ideal adversary for Jones in U.F.C. 285 on Saturday night: He was the reigning heavyweight champion when he and the U.F.C. parted ways. Instead, he watched the bout on television in his native Cameroon.
Ngannou saw Jones, a 35-year-old American, quickly dispatch the 32-year-old Frenchman Ciryl Gane, whom Ngannou beat in January 2022. Ngannou then saw Jones call out Stipe Miocic, his next opponent, who has also lost to Ngannou.
As Jones celebrated in the octagon, falling to his knees and praying while his family and coaches surrounded him, Ngannou wrote a congratulatory message, with a hint of sarcasm, to Jones on Twitter. It said: “Good job Jonny Boy. Sincerely, The heavyweight king.”
At his news conference after the fight, Jones insulted Ngannou in response, using a vulgarity to describe him.
The U.F.C. brands itself as a modern-day gladiator spectacle, but a highly publicized disagreement between Ngannou and the organization has kept fans from seeing the superfight that could have been.
On Saturday, Jones defeated Gane in the first round, submitting him via choke less than three minutes into a potential five-round competition. The victory crowned Jones as the heavyweight champion after he had ruled the 205-pound lightweight division for nearly a decade, and it positioned him for a new chapter in his storied but complicated career.
Gane was fighting Saturday as the next-best choice for an opponent. The contractual stalemate between Ngannou and the U.F.C., which most fans hoped would be resolved, is set to hang over the heavyweight division like a dark cloud.
Dana White, the U.F.C. president, said in January that the organization released Ngannou after two years of impasse in negotiations. On Saturday, in a news conference, he repeated that he would not try to sign Ngannou again and said that Jones would next face Miocic.
“If Francis doesn’t want the fight, you can’t make him fight,” White said. “And I doubt it would have gone any differently.”
Ngannou, who won the heavyweight championship after knocking out Miocic in 2021, defeated Gane via unanimous decision in 2022. It was the last fight on his deal, and leading up to it he openly discussed his desire for an increased salary and more flexibility to pursue boxing opportunities. White said Ngannou turned down an offer that would have made him the organization’s highest-paid heavyweight, a figure Ngannou said was around $8 million. While that is a large sum, it lags behind many boxers’ paydays. Ngannou said he also requested health insurance for all fighters, among other things.
In a phone interview Saturday afternoon, Ngannou said he was content with his decision.
“I always wanted to fight, and that’s a fight that I would love to have, but we’re not going to fight tonight because of the way that I saw things,” Ngannou said. “You have to give them a firm no and be decisive in what you want in order for the system to know that maybe something is getting done in the wrong way.”
Ngannou’s absence paved the way for Jones’s long-anticipated heavyweight debut to come against Gane. Jones entered the U.F.C. in 2008 and began an ascent rarely seen. He won the 205-pound light heavyweight belt in 2011 at age 23, becoming the U.F.C.’s youngest champion. He holds the record for most title fight wins (15), often deploying a skill set of elite striking, grappling and fight intelligence.
But Jones, at the peak of his career, committed actions that stained an otherwise prodigious résumé. The U.F.C. suspended him in 2015 and stripped him of his title after the authorities charged him with felony hit-and-run offenses in New Mexico. He pleaded guilty to leaving the scene of an accident and was sentenced to up to 18 months of probation.
He was suspended twice, in 2016 and 2018, for testing positive for banned substances by the United States Anti-Doping Agency. In 2021, he took a plea deal and avoided jail time for a domestic battery incident in Las Vegas involving his fiancée.
Jones said that he has revaluated the people around him and that his lifestyle has become calmer and simpler. He developed new hobbies, such as dog training and flying drones, and said in an interview last week that he felt he was in a “better place.”
“A lot of my young life was on a fast track,” he said. “Over the last two years, I’ve really got to evaluate my friends and the circle and my mentors, and I feel like I’m a product of my friendships these days. I’ve never been more proud of my team.”
Jones vacated the light heavyweight belt in 2020 to transition to heavyweight. He said that he would cut as many as 25 pounds during fight week and that he wanted to challenge himself against different opponents. He said he began weight training four times a week and adapted his diet to include more red meat, fish, chicken, rice and protein shakes.
During that time, he, like Ngannou, also bickered with the U.F.C. over increased pay. In March 2021, Jones wrote on Twitter, “Please just cut me already,” requesting that he be released by the organization. But the tone of the negotiations improved over time, Jones said, and the U.F.C. offered him a deal that made him feel “immediately respected.” Richard Schaefer, Jones’s representative, said in a January broadcast interview that Jones’s restructured contract most likely made him the second-highest-paid U.F.C. fighter behind McGregor.
“People argue — that’s just a part of life,” Jones said. “I don’t take this personal, and Dana doesn’t either.”
The body transformation sparked a seamless performance worthy of his higher salary. He took Gane down early in the first round Saturday and pinned him against the fence. He then transitioned to a guillotine front-side choke and squeezed until Gane tapped in submission.
Before White said he would no longer negotiate with Ngannou, Jones, in the interview Tuesday, said he would be open to the fight. He said that while the two shared different perspectives, he respected his approach.
“I’ve never seen a fighter leave the U.F.C. in such a great position,” Jones said. “It’s great for our sport to see that. It’s great to see guys walk away on their own terms.”
As for Ngannou, he said he was open to other options. He said he would like to arrange a boxing fight with Tyson Fury, the World Boxing Council heavyweight champion, or the former champion Deontay Wilder, and explore M.M.A. fights in other organizations.
“I have so much possibility, and to be free, like everything is available and possible for me,” Ngannou said. “I have my freedom, which is the most important thing. And I can do whatever I want, which, again, is very important.”