The 31-year-old actor has been honing his boxing skills for several years for his role as Adonis Creed in the newest films in the "Rocky"/"Creed" franchise, and recently bragged to TMZ.com that he'd hold his own against the 49-year-old ex-champion.
Roy, who is still active as a boxer and won a fight as recently as February, has now issued a challenge to Michael to back up his words with his fists and join him in the ring.
"If Michael B. wants this real, contact Roy Jones Jr. and we'll make it happen," he said in a video published by the U.S. gossip website. He advised the star to get his contact details from TMZ editors to arrange the fight.
Michael did admit that he'd have been no match for Roy in his prime - when the boxer became the first man in more than a century to win world championship belts in the middleweight and heavyweight divisions.
However, the veteran sportsman still believes he'd have the beating of his younger, fitter opponent - thanks to his experience and ringcraft - and added that he'd be ready for the fight with four or five weeks of training.
"I know he can't beat me still," he explained. "I know he's probably in better condition because he's younger... but I'm an old school vet."
Michael is currently on the promotional trail for "Creed II" in which he plays Adonis, the boxer son of Rocky Balboa's rival and friend Apollo Creed - who Sylvester Stallone's character fought in the original 1976 "Rocky" movie.
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If that’s what the fans want, y’all KNOW it’s not hard at all to make. Hard to get up early in the mornings, but sacrifice for the fans is a normality for me so just let me know. I’m not tripping either way. Delighted that he’s wanna be in with his top choice. Blessing to be that.
The first "Creed" movie relaunched the franchise to focus on Adonis - with Rocky taking on the role of his trainer. Directed by "Black Panther" filmmaker Ryan Coogler, it earned critical plaudits and was a box office hit - earning more than $170 million (£132 million).