Artur Beterbiev and Dmitry Bivol will finally step into the ring opposite each other on Saturday in Saudi Arabia.
Boxing fans have been waiting for years to see the light heavyweight world champions.
All four titles are on the line in Riyadh, with 39-year-old Beterbiev holding the WBC, WBO and IBF titles and 33-year-old Bivol the WBA (Super) champion.
Both men are undefeated and the match is being promoted as a potential classic in the making.
You can catch live text commentary of the main event and undercard, featuring two Britons in world title fights, on the BBC Sport website and app from 7pm BST on Saturday.
Who will become the first undisputed light heavyweight champion of the four-belt era? Who will suffer their first defeat? Could a draw be on the cards?
BBC Sport has asked the entire boxing world for predictions.
Retired world champion and boxing coach Anthony Crolla: “You can see what a good fight it is because so many people have a hard time picking a winner, and I’m one of them. If really pushed, I just don’t think Bivol will have the firepower to I see Beterbiev wearing him down and maybe getting a stoppage around the ninth or tenth round.
“But I also wouldn’t be surprised if we see a very disciplined performance from Bivol, outboxing Beterbiev, hitting him and moving him, similar to how he did against Saul ‘Canelo’ Alvarez.”
WBC lightweight champion Skye Nicolson: “It’s the typical brawler versus boxer, and I have to support the boxer. I find it hard to see Bivol getting caught in a situation he doesn’t want to be in. He’s so good at controlling the distance and pace of the fight.
“But if anyone can do it, it’s Beterbiev. My heart says Bivol.”
Retired world champion Barry Jones: “Beterbiev has to be a slight favourite. He has knocked out punchers, he has knocked out boxers and he can knock you out in the first round or the 12th. There is no round, second or minute where you are really safe with him.
But I still go for Bivol. I just feel that his intelligence, patience, discipline and calmness of approach could be just enough to get through the dangerous moments and get him through in a close decision.
“Bivol might have to get off the floor a few times, but I think he can get ahead early enough to sneak home.”
British Heavyweight Champion Fabio Wardley: “I’m leaning towards Bivol, but this is probably one of the hardest fights to predict in boxing right now. It’s a real pick-em fight with two guys with completely different styles. Beterbiev is a destroyer who can cut through anyone can. Bivol has done that too.” great strength, but is such a clean and accurate boxer.
“The question is who can best enforce their style on the night and make the impact.”
Heavyweight Frazer Clarke: “I keep changing my mind. I’ve said Beterbiev all the time, but I now think Bivol can handle this one. It’s a world-class 50/50, though.”
Retired world champion Darren Barker: “I would have Beterbiev as the favorite. When you have that power he knocks people down with punches. How can you not have him as the favorite? Not hugely, but at any time he can turn out the lights on Bivol. But I’m going to go in Bivol a unanimous decision, but a very exciting fight. What I mean by that is that the rounds will be enough. I’ll go with the matador in this fight, but I wouldn’t bet my house on it.’
Bivol’s promoter Eddie Hearn: “When you fight Beterbiev, it’s like a ticking time bomb. The speed of that time bomb depends on the opponent. Dmitry has the ability to make that tick very slowly. How slowly can he make it tick? The boom point is 12 rounds .
“Beterbiev is going to get you, but how quickly can he get you and how long do you have left if he gets you? The only person who can beat Beterbiev right now is Bivol.”
Former world champion Hannah Rankin: “This is a brilliant match-up of two fighters who have been waiting to fight for a long time and now all the marbles are on the line.
“I’m going with Bivol on points as he’s the younger and fresher of the two with less wear and tear on his body. However, I wouldn’t be surprised if Beterbiev drops Bivol during the fight.”
Saudi Welterweight Ziyad ‘Zizo’ Almaayouf: ‘Call me crazy, but I say Bivol is taking this very quickly. There will always be danger from Beterbiev, but I see that Bivol controls the distance too well.’
Former world champion Regis Prograis: “I have to bet on Bivol, he’s a beast. That’s a very good fight, the only bad thing is they don’t have any big names for people outside the boxing fans. But that’s a tough fight.”
Retired world title challenger Paul Smith: “From the beginning I said Beterbiev and I think it could be a late stop. I don’t think there is anyone who can keep him away from them. He is too ruthless.”
“Bivol is obviously exceptionally good and has incredible footwork, so I wouldn’t be surprised if he won. But I’ve always felt that, apart from Saul ‘Canelo’ Alvarez, Bivol has done just enough to win fights and that I am too.” I’m not sure that will be enough against Beterbiev. I don’t think he hits hard enough to earn Beterbiev’s respect.”
English cruiserweight champion Viddal Riley: “I’m going with Bivol. He has the better range of motion, better flow and will be able to outbox Beterbiev for the majority of the rounds. But as we get into the later rounds, it will be a war.”
