Zero and none -- those are the chances Tenshin Nasukawa has to beat Floyd Mayweather when they square off on New Year's Eve ... according to Roy Jones Jr.
"He's not gonna lose the fight."
Floyd and Tenshin -- an undefeated 20-year-old kickboxing superstar -- are fighting in Japan at the end of the month ... and there are some people who think Tenshin could be the guy to finally put Mayweather on the canvas.
Roy Jones, however, is not one of those people.
That said, Roy expects Tenshin to fare better than Conor McGregor -- because Tenshin is a seasoned stand-up fighter ... and "McGregor had never had a boxing match before in his life."
Floyd has said he'll make a 7-figure check for the 3-round exhibition match on Dec. 31 -- in a fight that will have no judges and won't go on either of their records.