Giro d'Italia winner Jai Hindley has tested positive to COVID-19, potentially dealing Australia's world road cycling championships campaign a massive blow.
The Australian team still hopes that Hindley will travel from his European base to join them in Wollongong for the September 25 elite men's road race, but for now they are unsure.
Hindley is a key member of the Australian team.
While Michael Matthews will most likely be their main protected rider, Hindley and Ben O'Connor could also feature prominently on the hilly road race course.
Team chief medical officer Dr Kevyn Hernandez said in an AusCycling statement that Hindley is "largely asymptomatic".
"Jai tested positive more than a week before the competition, but we will make a final decision on his participation closer to the event," he said.
"As with all events, we have a plan B and plan C, something all sporting teams need to have these days."
"At this stage, we're hoping Jai will be able to leave Europe on Monday to join the rest of the team in Wollongong mid-week."
As COVID-19 protocols are being relaxed, the Australian team has strict measures in place for the world championships.
At a team media conference on Friday ahead of Sunday's elite time trials, everyone attending had to wear masks, including the riders.
Hindley tested positive on September 12, a day after he finished 10th overall at the Vuelta a Espana.
In May, Hindley became only the second Australian after Cadel Evans's Tour de France triumph to win a three-week Grand Tour when he took out the Giro.
The worlds start on Sunday with the elite time trials, where Australian Grace Brown is a strong medal chance.
Brown finished fourth in the time trial at last year's Olympics and won the event last month at the Commonwealth Games.
She also won a stage earlier this week at the Ceratzit Challenge, held in conjunction with the men's Vuelta.
"This worlds is a big goal for me. When I set out my season, I had a big highlighter on Wollongong worlds - both the time trial and the (September 24) road race," she said.
"I know I'm up there and competitive at the top of the field, we'll see on Sunday where that lands me."
Three-time Commonwealth Games gold medallist Georgia Baker is also aiming for a top-10 finish, while Luke Plapp is unsure of his chances in the men's time trial after just finishing the Vuelta - his Grand Tour debut.