JOHANNESBURG, South Africa – Former President Nelson Mandela offered words of inspiration Monday to former heavyweight champion Lennox Lewis in an effort to soothe the boxer's bruised ego.

In a stunning upset, Lewis lost his WBC and IBF heavyweight titles to unheralded Hasim Rahman on a fifth-round knockout Sunday at the Carnival City casino in nearby Brakpan.

"I told Lennox that this is the nature of boxing. ... It is natural to have wins and losses," Mandela said, adding that Joe Louis had been defeated once, only to knock out Max Schmeling in the first round of their rematch.

Mandela, who once boxed, missed the fight but watched a replay.

"After seeing him, I felt like a young man," the 82-year-old Mandela said.

Lewis told a crowd of reporters gathered outside Mandela's home in Johannesburg that his defeat was "just one of those setbacks."

"He caught me with a lucky punch, but those things make boxing ... exciting," Lewis said. "One blow, then it's a completely different story."

Lewis said a rematch is guaranteed by contract, but has yet to be discussed.

Lewis shouldn't count on a rematch – never mind a $100 million showdown with Mike Tyson – promoter Frank Warren said Monday in London.

Warren said Lewis might be left out because Tyson is the WBC's mandatory challenger.

"I think Lennox has a problem now in getting the rematch," he said. "I'm sure there is a rematch clause but I think the WBC may step in and order Rahman to fight Tyson."

Warren has spent several months trying to arrange a Lewis-Tyson bout. But now that fight might never take place. Or, if it does, it could be for a much smaller purse.

"I'd been working on the finances for that fight and I was close to tabling an offer to both parties which I believed they would have accepted," Warren told BBC Radio 5 Live. "The venue would have been Las Vegas.

"I'm sure they (Lewis' representatives) will be doing their best to get the biggest payday they can – and that is going to be Mike Tyson. But Rahman has no ties with any TV company. He is free to do a deal with whoever he chooses.

"Lennox's management must work hard to make sure he gets his rematch. Otherwise, I can genuinely see Rahman fighting Tyson."