Lennox Lewis believes it would take something extraordinary for any of the 2019 heavyweight contenders to break the top three.
Lewis has been vocal that Anthony Joshua could do more to entice fights against Deontay Wilder and Tyson Fury.
But the former top division king – and the last man to be undisputed – see that trio ahead of the rest by some margin.
Naming the four fighters he thinks are next in line for a shot at the throne, Lewis cited the leading three sheer size as a huge factor.
“The way I see it, at the top of today’s current crop of top heavyweights is Anthony Joshua, Deontay Wilder, and Tyson Fury. Let’s call them the big three,” said Lewis.
“They are at the very top of the division, and then there’s everyone else. They can be interchangeable, yet still dangerous, opponents.
“You have (Dillian) Whyte, (Joseph) Parker, (Dominic) Breazeale, and (Luis) Ortiz. All of these guys are solid fighters that have the potential to break through with a great fight.
“However, one major difference is that they aren’t physically built like the big three. Heavyweight bodies have grown bigger, taller, and stronger over the years.
“To compete with or beat any of the big three, these fighters must fight them very smart.
“Physically, post-modern heavyweights have broken the mold from the days that 6-foot champions ruled the roost. Even my 6ft 5ins frame is on the shorter side of the top guys in today’s world.
“It’s getting harder and harder for the competition to physically match up with the big three, much like it was during the Klitschko era.
“The Klitschko’s dominated. This was through a combination of size, strength and skills. Which is a tough combination to beat.”
On who could reach similar heights in the future, Lewis named his trio to watch from the younger pack coming through.
“There are others who are also rising in the ranks, like Joe Joyce, Daniel Dubois, and Efe Ajagba. But they have not really cracked that top-tier plateau that’s going to drive pay-per-view ticket sales at this moment.
“Keep an eye out for them, though,” he added.
Joyce makes a step up against former WBC champion Bermane Stiverne on February 23, whilst Dubois is still making his way in the UK domestically.
The same can be said about 24-year-old Ajagba, who won all five of his bouts in 2018 via stoppage.
Ajagba begins his moves towards the higher ranks by facing Amir Mansour on March 9.