Mayweather's switch to octagon could prove biggest test

Undefeated boxer Floyd Mayweather Jr. of the U.S. poses for a photograph with his opponent Tenshin Nasukawa during a news conference to announce he is joining Japanese Mixed Martial Arts promotional company Rizin Fighting Federation, in Tokyo, Japan November 5, 2018. REUTERS/Issei Kato

TOKYO (Reuters) - Floyd Mayweather's route to boxing greatness has been carefully crafted without taking unnecessary risks, yet his announcement of a fight for a Japanese mixed martial arts organisation later this month could be his biggest gamble yet. 

Mayweather's last bout was a comprehensive boxing victory over Irish MMA star Conor McGregor in August 2017, but the American was back in the spotlight on Monday when he agreed to top the bill on the Rizin Fighting Federation's next card.