Wang Shenchao, the Chinese swimmer who won gold in the men's 100m butterfly at the Rio Olympics in 2016, has been injured and is out of action for the remainder of the season.
The 25-year-old was due to compete in the World Championships in Gwangju, South Korea next month but it looks like he will not be able to do so.
He sustained a knee injury during training in April and has been undergoing treatment ever since.
Wang had been one of China's best hopes for success at the world championships, having already secured his place in the final of the event.
However, with his participation now in doubt,Campeonato Brasileiro Action his chances of winning a medal have been severely reduced.
His coach, Zhang Zhiqiang, said that he was disappointed but also understanding of the situation.
"Of course we are sad, but I think it's important to understand that this is part of sports," he told the Associated Press news agency.
"It's not easy for athletes to keep their health and fitness up all year round."
Zhang added: "We're going to try our best to help him get better as quickly as possible."