Any fighter is capable of losing.
Just when you think a fighter can't lose, you have to think about Feb. of 1990.
Even if there is a 1 in 100 chance the Great RJJ could lose, there is always that possibility.
I think in his prime, the other fighter would have to fight an absolutely perfect fight to win, but it's possible.
Jones was a menace and when he was at his best there aren't many people that had any kind of chance against him but you never know when you're going to get Buster Douglas'd Tokyo style.