Not just a heavyweight battle against Fury in Riyadh, Usyk is also fighting for Ukraine's frontliners

Oleksandr Usyk may be the reigning WBA, WBO, IBF and IBO heavyweight world champion but to many the Ukrainian is the underdog going into Saturday's long-awaited unifying title fight with Tyson Fury in Riyadh.

Size matters, it seems, with southpaw Usyk conceding 15 centimetres (6 inches) in height to the 2.06 metre (6 foot 9 inch) Fury, 18cm in reach, and close to 22 kilos (49lbs) in weight.

And yet, he is not perturbed.

"To win this, I don't need to be heavy, I need to be fast, and quick," he told Ring magazine in February just before the Fury fight was postponed after the Briton picked up a cut in training.

"You never see a fat wolf in the forest."

It is easy to see Usyk as the lean wolf, cunning, quick and ruthlessly effective.

His perfect record of 21 wins and no defeats as a pro, 14 of those inside the distance, speaks for itself.

And apart from those three heavyweight belts he can also look back on a career that brought him Olympic gold in London in 2012 and the undisputed cruiserweight championship of the world.

Beyond the undoubted pedigree in the ring, he also has the fire within that a boxer desperately needs when he has reached the comfort of the mountain top.

The war in Ukraine, which followed Russia's invasion in February 2022, has ensured that.

It gave Usyk an extra dimension when he faced Anthony Joshua in Jeddah in August that year, almost a year after he had taken the Briton's titles in London.

"In the ninth round I realised that if I fall now, the spirit of the fighters who defend our country will also fall," he told AFP.

"I didn't box for myself, I boxed for all those who defend the country."

Eighteen months on from that fight and the Russians continue to wage war on Ukraine, adding fuel to the Usyk fire.

In some ways, it marks a shift in perception of the 37-year-old who also beat Daniel Dubois in Poland last August.

Born in the Crimean town of Simferopol, he was accused by many Ukrainians of sitting on the fence over Russia's annexation of the peninsular in 2014 and castigated for saying that Russians and Ukrainians were the same people.

Since Russia's 2022 invasion however the tune has changed with promoter Alexander Krassyuk saying that Usyk "is the real inspiration for Ukraine, for the guys on the frontline".

"When he speaks, these words inspire the Ukraine people and the soldiers to fight the enemy and to have courage," Krassyuk told ProBox TV in August last year.

"Usyk is not fighting for himself anymore."

Usyk has felt the war close up. Immediately after the invasion he returned to Kyiv and spent time on patrol.

Then his former teammate Oleksiy Dzhunkivskyi was shot dead by the Russians.

He was persuaded, however, to return to the ring, to fight the war in a more public arena.

"The guys from the armed forces convinced me that I need to prepare and fight to help my country on the international stage, talk about it and bring opportunities to Ukraine to restore my country," he told said.

Beyond that, though, Usyk is aware of history calling in the ring.