Floyd and Tenshin Nasukawa in the ring [Photo: Courtesy]

Floyd Mayweather ruled out a boxing comeback following his first round knock-out win over Tenshin Nasukawa in an exhibition fight in Japan.

The 41-year-old American floored his 20-year-old opponent THREE times inside the opening round, prompting Nasukawa's corner to throw the towel in.

Nasukawa was reduced to tears as he came to terms with the speed in which he was dispatched by "Money" Mayweather, who earned a tidy $9million for his troubles.

Speaking about his future in the sport after the fight, Mayweather ruled out a possible comeback. He said: "I want to say thank you to Tenshin. This don't go on our record. We are both still undefeated.

"He is a great champion and a great fighter. I am still retired, I don't look to come back to boxing. I came back for entertainment for the people of Japan."

Nasukawa came out tentatively when the bell sounded and the fight got underway in Tokyo, while Mayweather smiled and threw his arms about wildly.

The Japanese fighter then caught the American with a decent shot, prompting Mayweather to burst into life and take the fight seriously.

What followed was a boxing lesson as Pretty Boy Floyd landed heavy punch after heavy punch, knocking his opponent to the canvas with ease.

Nasukawa needed time to recover, but Mayweather continued to swarm, and moments before the bell rang to end the first round his corner threw in the towel.

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