Gennady Golovkin stops Ryōta Murata in nine to unify middleweight belts

• Golovkin, 40, stops Murata at Japan's Saitama Super Arena
• Third fight with Canelo Alvarez in September could be next

Gennady Golovkin became the unified world middleweight champion with a ninth-round stoppage of Japanese fighter Ryta Murata on Saturday.

The Kazakh boxer Golovkin, who turned 40 on Friday, sent his opponent to the canvas with a big right hand and Murata's corner threw in a towel.