Johnny Nelson and Spencer Oliver have previewed tonight's showdown between Anthony Joshua and Oleksandr Usyk.
The pair collide at the Tottenham Hotspur Stadium with Joshua making the second defence of his second reign as unified heavyweight champion.
Usyk - the WBO mandatory challenger - enters his third fight at the weight following his dominance at 200lbs.
The Ukrainian southpaw won the inaugural 2018 World Boxing Super Series and became undisputed champion at cruiserweight in the process.
Since then, Usyk retired Tony Bellew in Manchester and has fought Chazz Witherspoon and Derek Chisora. Should he win, he'll do something only Evander Holyfield has done - unify the cruiserweight and heavyweight divisions.
While the odds are stacked against him due to the size, reach and punching prowess of Joshua, Nelson and Oliver - who are working together on BoxFit, an app that encourages people to train alongside them virtually - believe Joshua has his toughest test to date.
"On paper you got to look at that and in reality, Joshua is fighting a live opponent with a champions mentality - he's dominated the cruiserweight division and stepped up at heavyweight," Nelson told Planet Sport.
"The general public do not realise how good of a win this would be for Joshua pulling off the win because Usyk is a class act. That way, Joshua would have ticked off every box in shape and size and hopefully, he will beat him and get the credit he deserves.
Oliver added: "It's a big test for Joshua. Your hardcore boxing fans will recognise that but the general public won't recognise how good a fighter Oleksandr Usyk is. When we go back to 2013 he was a super heavyweight as an amateur - he beat Joe Joyce at the York Hall - so he knows how to handle the big guys and Joshua respects that."
Nelson - the longest-reigning world champion at cruiserweight as WBO king from 1999 to 2005 - made the transition from 200lbs to heavyweight himself and believes Usyk will need to apply pressure to Joshua straight away.
"I just watched a fight now in Evander Holyfield's first fight against James Tillis and people said he's too small, he's stepping up and his speed and footwork - he did it.
"So the idea is to draw your heavyweight out to make them work harder than they would normally work. That's what Usyk's got to do - he's got to make him work."
Oliver - a former European champion who is now a respected analyst and is heard on Pound for Pound podcast alongside Jake Wood - is backing Joshua inside six rounds but should it go past six, then it's Usyk's to win.
"I don't think he needs to go to the distance he needs to take Joshua into the later rounds and if he sets a hard pace early and makes Joshua work then he'll be looking for either a points victory or a late stoppage. You know you have a great fight by the way when everybody has an opinion but nobody knows.
"When you look at the great fighters who have come up from cruiserweight like Michael Moorer - he was a great light heavyweight, cruiserweight, who come up and won at heavyweight.
"Evander Holyfield - if you look at those greats Usyk falls into that category and if Usyk can do that and beat Joshua - as Johnny said, a lot of good cruiserweights can beat heavyweights but they don't beat the top tier. Some of them do and Usyk can fall into that category," Oliver added.