Michael Matthews has been ruled out of the Tour de France after team doctors discovered signs of a pulmonary embolism in mid-June.
The Australian cycling star was also ordered to cease all physical activity.
A pulmonary embolism is a blood clot that goes to the lungs and blocks an artery, which restricts blood flow.
If untreated, it can be life-threatening.
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The Jayco AlUla rider was at an altitude training camp when doctors first detected signs of the issue.
"The medical team are now thoroughly investigating the extent of the issue and possible cause, to define a safe and optimal recovery process for the athlete," a team statement read.
"During this period of investigation, as a safeguarding measure, Matthews will refrain from competition to ensure there is no risk to his health and well-being, therefore ruling out his participation in the upcoming Tour de France."
In his career thus far, Matthews has won four stages at the Tour de France.
He earned his first win of the 2025 season in May at the Eschborn-Frankfurt one-day race in Germany.
The 34-year-old's cycling career is on standby for the moment, although Matthews has declared he "will make a full recovery".
"Thank you everyone for the kind messages, I will get around to replying to you all, just taking a few days to process the news but my condition is OK and I will make a full recovery, it will just take some time," he wrote on Instagram.
"Thank you all."
Ben O'Connor, Luke Plapp, Luke Durbridge, Eddie Dunbar, Mauro Schmid, Dylan Groenewegen, Luka Mezgec and Elmar Reinders will make up Jayco AlUla's line-up for the upcoming Tour de France.