Almost 21 years after his first appearance inside the Octagon, Vitor Belfort will fight the last bout on his UFC contract Sunday, taking on Uriah Hall in the co-main event of UFC St. Louis.

“The Phenom” expected his UFC 212 clash with Nate Marquardt in June to be his last under the company’s banner, but found out days before the event that he still had one bout left in his deal. Victorious in Rio de Janeiro, Belfort explains why he will retire Sunday night.

“I will start to open my gym franchises on Monday,” Belfort told Brazilian reporters in an online scrum on Thursday. “I’m investing in my businesses. I think it’s time to rest my body, so I’m focused on the franchises of Belfort Fitness and Lifestyle, not only in the United States but also in Brazil.”

Staying retired is always complicated, especially in a sport like mixed martial arts, and “The Phenom” already has a price in mind for a potential return to competition — inside or outside the UFC.

“$10 million or more, to start the conversation,” Belfort said. “That’s the number. And then we start talking.

“A lot of money. A lot of money. Many millions,” he continued. “Anyway, I will always train and dedicate myself. I have a lot of friends fighting, so I will always be prepared because I love doing this, this is my lifestyle, but it has to be very, very, very interesting because I’m happy with this decision.”

Belfort was part of some historical events under the UFC banner, fighting for the title in multiple weight classes, winning a heavyweight tournament and holding the 205-pound belt at one point of his career, and he doesn’t mind ending his career on a Fight Night card in St. Louis.

“It’s wonderful,” he said. “There’s no such thing as big or small card for me. When the Octagon closes, it’s the same size, and it’s a joy for me to be there. I don’t like to say goodbye, to do a party for a farewell fight. This is not soccer. It’s not a farewell fight with barbecue and music.

”My friend, this is a fight, you can’t relax and enjoy, say goodbye. This is a very serious sport, so it’s a pleasure for me to be here. It’s a good card, full of champions, beasts, the future of the sport. I’m very happy with everything I’ve accomplished, what I’ve done, and being able to end like this. I’m feeling special.”