First off, DJ says Floyd is the one guy he would NEVER bet against in a fight -- "because he's just that good."
So, the respect is there.
But, now that Floyd's in the exhibition business -- where he's taking 3-round fights in Japan for roughly $10 mil-a-pop -- would Johnson be interested in testing his boxing skills against the best ever?
"Absolutely, I'll step in there and fight Floyd," 32-year-old Johnson said ... "3 rounds? Just boxing? I'll do that. It'll be fun! I feel like I'll do fine."
And, this isn't one of those hypothetical matchups either -- because as Johnson put it, "I think for Floyd Mayweather if it makes money sense, I think he would do anything."
Mayweather has already proven to be a big draw in Asia -- and with Johnson now fighting in Japan, his popularity is expected to skyrocket there too.
And, if DJ wins his March 31 fight against Yuya Wakamatsu at "ONE Championship: A New Era" -- it'll only help to create interest.
Of course, Johnson is one of the greatest MMA fighters of all time -- the former UFC flyweight champ who racked up the most consecutive title defenses in UFC history with 11 in a row.