In what is already shaping up to become one of the great boxing rivalries, perhaps one day joining the likes of Pacquiao and Marquez or Ali and Foreman, heavyweight champions Oleksandr Usyk and Tyson Fury will on Saturday night face off in Riyadh, Saudi Arabia, with the undisputed heavyweight championship of the world on the line.

Earlier this year, Ukraine's Usyk inflicted the British champion's first career defeat in a split decision based on points. That match unified boxing's various championship belts in the first undisputed title fight since 1999, when Lennox Lewis beat Evander Holyfield before being stripped of one of the belts in 2000. The rematch has become one of the most fiercely anticipated bouts in decades, with British media reporting a prize purse of £150 million ($190 million), of which Usyk is expected to receive the bigger share.

However, perhaps the most unique thing about this match will be the common bond the two men share. In a sport dominated by excess and violence, they have both become well known for their willingness to talk openly about their Christian faith and the central role it has played in their lives.

Speaking with boxing reporter Steve Bunce in the lead-up to their last fight, Fury spoke about the faith both he and his opponent share.

"We are the two biggest Christians in boxing," Fury said. "Without failure, I can train all I want, but whoever God wants to win this fight will win. It doesn't matter if you're from the gutter or the kingdom of wherever.

"Listen, being a champion is great. But to see someone who is also a world champion and has big faith in God is unbelievable. Beautiful."

A sometimes controversial figure, Fury's discussions of his faith have often been raw and honest, reflecting a man who has struggled with mental health issues and substance abuse. Speaking to Rolling Stone magazine in the aftermath of a positive drug test almost a decade ago, Fury revealed his parlous mental state and how his faith had kept him from falling over the edge.

"I stopped it all on the first of the month," he said in response to whether he was still taking cocaine. "I'm trying to forget about it all. I'm putting boxing behind me, the drinking, the drugs, just getting back in the church and right with God."

While he still has his brushes with trouble, Fury has carved out a remarkable redemption story, becoming an advocate for mental health and being recognised as an undefeated champion after beating Deontay Wilder in 2019.

"I would like to say thank you to my Lord and Saviour Jesus Christ. In the mighty name of Jesus, I won this fight tonight again," Fury said in a post-match interview after their 2021 rematch. "I give Him the glory; He gives me the victory."

Usyk is a much more quietly spoken champion than the brash Tyson, but has been just as open about the importance of his faith.

After winning his last bout against Fury, and claiming the heavyweight crown, Usyk's first act after the bell was to ask his trainer to hold a crucifix to his lips.

"It was a present from the chief monk at one of the monasteries that I go to," the devout Orthodox Christian said, speaking to the Sunday Times. "It gave me strength and led me to victory. When I touched it, I felt the love of God."

He went on to reveal he is aware of some of the contradictions some might see in a Christian pursuing such a violent path.

"I see myself as a sinner. I needed his help to overcome my sins," he said, only for the interviewer to ask what sins he was referring to.

"That main one was that I was hitting a man in the face."

Their different approaches have led to some prickly interactions, with the notoriously voluble Fury trying to rattle Usyk with some traditional boxing trash talk, but the Ukrainian continues to refuse to engage in aggression outside the ring. It is clear, though, that beneath the PR stunts and marketing displays that sell tickets, the two men share a deep admiration for each other.

"Tyson now speaks less than he used to. Maybe he has changed," Usyk said. "I have no anger towards him, only respect."