Ryunosuke Haga, a bronze medalist in judo at the Rio Olympics, underwent surgery last week on a dislocated joint in his left shoulder, the All Japan Judo Federation said Wednesday.
Haga, who finished third in the men's 100-kg division at the 2016 games in Brazil, will be sidelined for about six months.
The 26-year-old hurt his shoulder during February's Dusseldorf Judo Grand Slam and will sit out next month's national invitational weight class championships.
Japan's Aaron Wolf, the reigning world champion in the men's 100 kg, will also miss the April tournament due to a knee injury.