Fury-Usyk clash in Saudi will define the world heavyweight championship of the century

Victory for either Oleksandr Usyk or Tyson Fury on Saturday will create the first undisputed heavyweight champion of the world in 24 years.

The ever-bubbling alphabet soup of boxing sanctioning bodies -- a winner in Riyadh would become the first four-belt heavyweight champion -- means that becoming, and remaining, undisputed champion requires not just skill and toughness in the ring, but acumen outside it.

When asked if he would like to say anything at the official weigh-in Usyk shrugged his shoulders and said: “Let your hands talk in the ring. I am excited … let’s make history."

A winner will join a select group. Here AFP Sport picks six of the undisputed best.

Hard-hitting Dempsey

The hard-hitting and aggressive Jack Dempsey became the first official world champion at the start of 1921 when the American National Boxing Association and the powerful New York State Athletic Commission agreed to recognise a world champion.

The "Manassa Mauler", with a right nicknamed "Iron Mike" and a left hook dubbed "Big Bertha" had become 'lineal' world champion, in boxing parlance "Beating The Man to become The Man" when he bludgeoned Jess Willard in 1919.

But the newly-minted official status helped turn his first sanctioned defence, against Frenchman Georges Carpentier, into the first "million-dollar fight". He defended his title twice more, before losing twice to Gene Tunney and retiring.

The Joe Louis era

After the first African American heavyweight champion, Jack Johnson lost to Willard in 1915, no black boxer fought for the title until 1937, because Joe Louis, who had just lost to Max Schmeling was a more palatable challenger for Cinderella Man James Braddock's title than the German.

Louis knocked out Braddock to claim a title he held for record 26 defences over more than 12 years. The most famous was the first-round revenge demolition of Schmeling at Yankee Stadium in 1938. Louis was smart, calm, technically sound, and packed a ferocious punch. "Everyone has a plan until they've been hit," he said.

Rein of the Rock

After war service, an undistinguished amateur career and a baseball tryout with the Chicago Cubs, the boxer, who changed his name from Rocco Marchegiano, turned professional just before his 25th birthday in 1948.

He fought 49 times as a pro, winning every fight, 43 of them by knockout. Only 5-foot-10, Marciano was relentless, resilient and a thunderous puncher. He was 29 when he got his title shot, flooring Jersey Joe Walcott in the last round with a straight right: his "Suzie Q".

Having pummelled an ageing Louis on his way up, knocked out the 39-year-old Walcott in the first round of their rematch, Marciano quit for good at 32 after stopping 42-year-old Archie Moore.

Enter the Greatest

The Greatest only fails to match Louis for total defences because he was effectively banned from boxing from March 1967 to October 1970, for his opposition to the military draft.

The Louisville Lip, who later declared "I'm so mean, I make medicine sick", had already upset the American establishment by changing his "white man's name", Cassius Clay.

After toppling Sonny Liston to win the title at 22 in 1962, he lost his undisputed status for taking a rematch with Liston. Ali defended his remaining titles seven times, before reunifying the division in 1966 against Ernie Terrell.

At 25 he was banned. Ali was 29 by the time he got his crack at regaining his world titles, against Joe Frazier in 1971, but suffered his first loss. It took until 1974, and his victory over George Foreman in the "Rumble in the Jungle", a fight that highlighted Ali's craft, cunning and courage, to reclaim his crowns.