Muhammad Ali will forever be remembered as the greatest heavyweight - indeed boxer - that there ever was after capturing the imagination of the public for his performances both in and out of the ring.
For the heavyweight champions that have followed him, Ali was the most impossible of acts to follow and bubbling beneath the surface of their careers was always the question of how they would have done against "The Greatest".
Here, we pit Ali against some of the fighters that came after him, and ask boxing experts Phil Barnett and Mark Staniforth to imagine what might have happened...
Muhammad Ali v Mike Tyson
PB: Tyson causes Ali problems with his squat, bobbing style and tests the taller man's chin in the early-middle rounds. Keeping his composure, Ali adjusts to Tyson's frenetic aggression to keep the New Yorker at arm's length working the jab and counter right hand. Ali split decision.
MS: Ali saved his best performances for the biggest punchers - the way he took apart Cleveland Williams, and rope-a-doped George Foreman. He would have too much movement and too many brains for even a peak Tyson - and do what Buster Douglas did, only better - teasing and frustrating Tyson till the end came somewhere in the mid to late rounds. Ali KO.
Muhammad Ali v Lennox Lewis
PB: Wary of Lewis' jab, Ali has to utilise his head movement to avoid the Briton's ram-rod while landing scoring punches of his own. Lewis' sound orthodox skills keep him in the fight but Ali is always in control, with his footwork easing him in and out of range. Ali unanimous decision.
MS: Lumbering Lewis would no doubt lose some weight in order to combat Ali's elusiveness - thereby negating his single biggest advantage. Ali would be faster on the draw through and remain largely untroubled by the signposted lunges Lewis could summon. Still, Lewis would at least make it look competitive, before succumbing widely on points. Ali unanimous decision.
Muhammad Ali v Evander Holyfield
PB: Holyfield's ring nous and wily intelligence gives him some success against the naturally bigger Ali. However, Ali is a level above and as the fight becomes increasingly one-sided, Holyfield's face is left a mess from the constant peppering of jabs and right hands. Ali unanimous decision.
MS: Arguably the modern fighter against whom Ali would have most trouble. Just as he struggled to figure out Ken Norton, Ali would be discomfited by Holyfield's head-first persistence, and take some time to figure out his opponent in a fight unlikely to be easy on the eye. Ali, bulked up for extra strength, would likely slug his way to an unconvincing points win. Ali unanimous decision.
Muhammad Ali v Vitali Klitschko
PB: The older Klitschko is more resolute than his supposedly 'chinny' brother but also slower and more predictable. Aside from being caught with an occasional jab, Ali's speed and variety earn him a comfortable points win. Ali unanimous decision.
MS: Klitschko's sheer size would present the major problem for Ali, but his upright orthodoxy would hardly make him an unsolvable riddle for a champion blessed with such physical dexterity. He might be wobbled - he might even briefly hit the canvas if he allowed his eagerness to get the better of him - but there can be little disputing that Ali would recover and win comfortably on points. Ali unanimous decision.
Muhammad Ali v Wladimir Klitschko
PB: Ali is wary of Klitschko's size and power and avoids the Ukrainian's stiff lead left hand, while Klitschko never even comes close to landing his booming right. Ali toys with Klitschko before a counter right hand scrambles the European's senses and the left hook leaves him down and out. Ali KO.
MS: The younger Klitschko could pose Ali a sterner threat, but it somehow seems the type of fight which would bring out the greatest in "The Greatest". Klitschko has come a long way since his early knockout losses, but the likelihood is Ali would surprise him by coming in light and clinical, keeping Klitschko at range before delivering the knockout blow somewhere around round eight. Ali KO.
Muhammad Ali v David Haye
PB: Haye begins typically cautiously as Ali dictates the fight from the off, with the Englishman's speed still not enough to be quicker than Ali. Increasingly desperate, Haye lands an overhand right, which only serves to prompt Ali to bring the fight to an end with a brutal stoppage of the hugely over-matched Englishman. Ali KO.
MS: In the unlikely event that Haye was bestowed the honour of sharing the same ring as Ali, he would be wise to make the most of his moment. Ali would win at will. He would probably appreciate his brashness, and on that basis alone might allow the bout to stretch somewhere towards its second half before the inevitable conclusion. Ali KO.