The 34-year-old Australian cycling star Michael Matthews has been hit by a blood clot in the lung and will miss the Tour de France in July.
The blood clot was discovered during a high-altitude camp recently.
"Matthews' health condition is stable. The medical team is now carefully investigating the extent of the problem and a possible cause," his team Jayco Alula writes in a press release.
It is not known when Matthews can return.
Matthews has four stage wins in the Tour de France, the latest in 2022.
The French cycling classic starts on July 5.