Floyd Mayweather doesn’t take these exhibitions too seriously. He doesn’t have to. The 45-year-old Hall of Famer is scheduled to face mixed martial artist Mikuru Asakura in a pay-per-view boxing exhibition Sunday in Saitama, Japan (Saturday in U.S.). He was asked at a recent news conference how he prepares for such “fights.” He doesn’t do much. “We don’t train as much as we did when we were competing,” said Mayweather, referring to his actual boxing career. “When we were competing, we were competing against the biggest and best in the sport of boxing. “Now we do a little. We may…