Andrew Berto says Tenshin Nasukawa has a huge chance ... the chance to ruin Floyd Mayweather's legacy FOREVER, all he's gotta do is go in there and beat Floyd.
Mayweather is 50-0 and has beaten everyone from Canelo Alvarez to Oscar De La Hoya ... but, according to Berto, that all goes out the window if he loses his December 31 exhibition match with Tenshin.
"It would tarnish it for sure. You cant be 50-0 fighting some of the best fighters in the world then get knocked out by some kid.