According to Floyd Mayweather, he barely trained at all for his one-sided first-round knockout victory in a mismatched exhibition fight against Tenshin Nasukawa in Saitama.

Mayweather rocked up to the arena late, causing a 90-minute delay to the scheduled fight time, with a flooded hotel lobby blamed for his delayed arrival.

But he soon made up for lost time, knocking down his opponent twice before flooring him for a third and final time with a fierce right as the three-round exhibition, which was truthfully a pretty farcical affair, came to an abrupt end with around 40 seconds left in the first.

Undefeated kickboxer Nasukawa, who had vowed to "take down Mayweather" was left in tears in the ring but was hailed by his opponent, who claimed on Instagram he will earn $9 million for the bout.

"I want to say thank you to Tenshin, it's about entertainment," Mayweather said in the ring. "Tenshin is still undefeated, I did this just to entertain the fans.

"I said, 'Why not?'. I'm still retired, still 50-0. Tenshin is a true champion and a hell of a fighter. Tenshin, hold your head up high, I want fans around the world to support Tenshin, he's a great guy and a great champion."

And Mayweather would later reveal that he barely trained at all for the contest.

“Did I have a training camp for this fight? No,” Mayweather said during the post-fight press conference via Bloody Elbow. “I went to the gym a few times and moved around with Daquan (Mays), a young champion on the rise. Now, I’mma call him a champion now — he could be a champion, which I believe he can, with experience, and if he listens. He’s young, he has a lot to learn, but he will be okay.

“I’m just happy he was able to move around with me, just a little bit, just to get the kinks out, so I can come out here and perform for you guys.”