Former WBO minimumweight champion Ryuya Yamanaka is set to call time on his boxing career due to subdural bleeding, sources familiar with the matter said Friday.

According to the sources, an official announcement on the retirement of the 23-year-old Japanese, who relinquished his title to Filipino challenger Vic Saludar last month, is expected to be made early next week.

Under Japan Boxing Commission regulations, if a commission physician determines a boxer suffered any degree of cerebral hemorrhage during training sessions or fights, his license automatically becomes invalidated.

Yamanaka made his pro debut in June 2012 and was crowned WBO minimumweight champion in August 2017, taking the title off fellow Japanese Tatsuya Fukuhara. He has 16 wins, including five by knockout, and three losses in 19 bouts over his career.