Japanese rugby player, Amanaki Mafi who is a former player of the Melbourne Rebels has been fined NZ$50,000 and discharged without conviction after a late night bust-up with a former Melbourne Rebels team-mate in July.

Mafi pleaded guilty to assault with intent to injure Lopeti Timani, who he has known since they were children growing up in Tonga.

The two that went to the home of a family member of Mafi, after they lost to the Highlanders in Dunedin on July 14 and were drinking into the early hours of the next morning and became intoxicated.

Mafi became enraged after Timani used an offensive word in front of a female relative, and challenged him to a fight.

Mafi will have to pay NZ$50,000, which includes Timani's fine and NZ$20,000 in medical expenses.

He was selected in Japan's World Cup squad, but missed the opening win over Russia because of a shoulder injury he suffered in their final warm-up game against South Africa.

He recovered to play two games, with the Brave Blossoms losing the quarter-final against 2019 Rugby World Cup champion, South Africa.