Giro d'Italia leader Remco Evenepoel was forced to pull out of the race late Sunday after contracting Covid-19, gifting Geraint Thomas the pink jersey as the new overall leader.
The dramatic news came just hours after Evenepoel had reclaimed the overall lead by winning the 35km stage nine individual time-trial from Thomas.
"I am really sorry to be leaving the race. As part of the team's protocol, I took a routine test, which unfortunately was positive," said the world champion in a team statement.
His forced withdrawal is a bitter blow for the 23-year-old Belgian, who was the favourite to add the Giro to his Vuelta a Espana victory.
"My experience here has been really special and I was looking forward to competing over the next two weeks," Evenepoel added.
"I can't thank enough the staff and the riders who sacrificed so much in preparation for the Giro. I will be cheering them on over the next two weeks," added he rider who will travel home on Monday by car.
Soudal Quick-Step said that all their other riders and staff tested negative.
The shock news left Ineos Grenadier's Thomas, adrift 45sec before Evenepoel's exit, heading the general classification by two seconds from Primoz Roglic ahead of Monday's rest day.
The biggest surprise of the tricky stage nine was the 2018 Tour de France champion Thomas who timed 41min 25sec, one second slower than Evenepoel but one second faster than his Ineos teammate Teo Geoghegan Hart.
Thomas won the 2020 Giro time trial in Sicily only to crash out a few days later as Hart went on to lift the title.
Hart is now third in the standings with Joao Almeida in fourth.
"That was close. It was good to be in the mix with Tao. It looks promising," said the 36-year-old Welshman before news of Evenepoel's positive test.
In the stage, riders were forced into a prudent approach given the rain-slick urban streets and cobbled surfaces as the top five on the day were separated by just eight seconds.
Team UAE leader Almeida also felt he could have done better.
"With the rain it was slippy," he said. "With all the corners it was a gamble. All in all I was happy though," said the Portuguese rider.
Another man who had been tipped to win on this pizza-flat route was Ineos speed king Filippo Ganna, who pulled out ahead of Saturday's stage, also with Covid.
Overnight leader, Norway's Andreas Leknessund made a valiant effort to retain his pink jersey, but dropped to sixth, now fifth, overall.
As Evenepoel heads home, the peloton gets its first rest day on Monday before two mountain and three hilly stages in week two with the race veering into Switzerland where the Crans Montana and the Col du Grand Saint Bernard at 2469m altitude await any pretender to this 106th Giro.