Campbell and Joshua have maintained a close friendship since the latter turned professional in July 2014 after signing for Eddie Hearn's Matchroom stable.
Despite this, however, Campbell still errs on the side of caution, although he expects Joshua will ultimately prove to be too 'strong' for Usyk.
“I think it’s a great fight, Usyk is an unbelievable talent,” he told The Mirror. “His technique and boxing IQ is certainly up there with the best, but is he a heavyweight?
“I don’t think he’s quite a heavyweight to be honest, this is where Joshua has the advantage.
“Joshua has got quick hands, and is a big strong heavyweight, so if he imposes his strengths I think he will win the fight.
“If he sits off, it could be Usyk’s night, and I can’t see Usyk wanting to get involved in a big strong heavyweight like Joshua.
"So his tactics will mostly be to make him miss, move around and Joshua has to put it on him.”
Campbell (20-4, 16 KOs), who recently announced his retirement from professional boxing, also stated that winning a gold medal in front of a raucous home crowd was the greatest achievement of his career.
"The Olympic gold medal was massive for me," the 33-year-old said.
"I was going to retire after the Olympics, as it was my dream to become Olympic champion and I successfully done it.
"I first thought well I haven't got any more so I will retire.
"It gave me a huge professional platform to turn professional, I was then on the radars for the professional promoters.
"It gave me a fantastic opportunity."
The former two-time lightweight world title challenger also discussed his plans for a career change after retiring from boxing, stating his desire to become a ringside analyst.
“I’d definitely like to keep a bit of skin in the game of boxing, I love boxing,” he added.
“And I am quite knowledgeable about it, I would love to do a bit of commentary here and there.
“But aside from that, I have a gym built in the city centre called 'Coolhand Fit24' and the memberships are building very well for that, it has a bright future."News Now - Sport News