Deontay Wilder and Oleksandr Usyk could contest the undisputed championship because they pose serious threats to Tyson Fury and Anthony Joshua, says Shannon Briggs.
Joshua and Fury's plan to decide every major belt in the heavyweight division was interrupted - Fury will now defend his WBC belt in a trilogy with Wilder, while IBF, WBA and WBO champion Joshua was ordered to take on his mandatory challenger Usyk.
Briggs, a former world heavyweight champion, has now warned Joshua and Fury's hope to reschedule their mega-fight could be in tatters if they do not take their upcoming fights seriously.
"Don't sleep on Wilder," Briggs tells Sky Sports.
"Throughout the history of the boxing world, he is a freak of nature.
"He could crack anybody and knock them out with his power.
"He will be an underrated guy for a long time because he didn't have a lot of guys to fight.
"We don't know what he will come with in this fight. He might shock the world!"
After a draw in their first fight, Fury emphatically stopped Wilder to rip away the WBC belt and inflict a first defeat on his rival.
A court of arbitration ruled they must meet again and a date of July 24 has been set in Las Vegas.
"Fury might have got the wrong idea.
"If this guy knocks out Fury, then what?
"It is possible. Will there be a fourth fight?
"Fury can't sleep on Wilder. We've got to look at this for what it is - a 200lbs man? With those skinny legs he shouldn't hit that hard!
"But he hits sickly hard. It isn't normal to hit that hard. But he can't fight backing up."
Joshua was ordered by the WBO to defend his belt against mandatory challenger Usyk. They have until May 31 to agree terms before purse bids will be used to confirm the fight.
Briggs warned: "The fight to get ready for is Usyk vs Wilder!
"We might have to get ready for that."
He says about Usyk, the former undisputed cruiserweight champion: "Tough, tough, tough fight. A guy like that? Who can work like that?
"He is a king-sized Vasiliy Lomachenko!
"As the rounds go on, he gets stronger.
"The best chance for AJ is to catch him early. AJ is strong early, Usyk is strong late.
"This is a dangerous fight, a tough fight. This Usyk is different, man.
"This is AJ's toughest fight - equally as tough as AJ vs Fury.
"If the ring is big, he will be hard to catch. He gets stronger as the rounds go on so, what happens is, he starts pushing you downhill.
"He has work rate and he's southpaw. He can sneak shots in. He has so much energy, he throws so many punches which aren't all hurting you, but it's the punches that you don't see.
"His condition goes up and up, and he runs you into the ground."
Usyk was previously in talks to fight Joe Joyce for the WBO interim belt.
Briggs says: "The only man I see similar to him is Joyce. He gets stronger and stronger and stronger. He is a super threat.
"Joyce is different. He's a big oaf, a big geezer, a big joker!
"He's not normal. No geezer with that type of size should be able to flip around like that, to control his body weight.
"No man I've seen can jump in the air and flip around - that shows me that his core strength is beyond strong.
"That will help with your chin and your neck. Everything is connected.
"He is super strong."
'Let's go champ!'
The American won the WBO title in 2006 against Siarhei Liakhovich. He lost WBC title fights to Lennox Lewis and Vitali Klitschko.
Briggs spent the latter part of his career chasing Wladimir Klitschko, and then David Haye, and trying to publicly goad them into fights but to no avail.
"I was at max a four-round fighter - I could stretch that out at times," he says.
"I've got the most knockouts in heavyweight history in the first round. I was a fast starter.
"I told my mother, aged 15 or 16: 'I think I can make it in boxing'.
"She said: 'If I buy you these boots you've got to promise to knock them all out in the first round because you've got asthma!'"