Race favourite Tadej Pogacar was on Thursday hailed as "unbeatable" even as he revealed he contracted Covid just 10 days ago.

Winner of the 2020 and 2021 Tour de France, the Slovenian won the Giro d'Italia last month and is hoping to become the first rider since Marco Pantani in 1998 -- the year Pogacar was born -- to win the rare combination of a Tour-Giro double.

"The Giro-Tour double is difficult to achieve. It's a big challenge but I'm ready to take it on," the Team UAE rider said Thursday.

The challenge will be made even tougher by the presence in the peloton of two-time defending champion Jonas Vingegaard, the Dane who pushed him into the runner-up spot in the past two editions, as well as two other leading contenders, Primoz Roglic and Remco Evenepoel.

Belgian rider Evenepoel deemed Pogacar "unbeatable" if he remains "safe and sound" but that dose of Covid may just have sapped some of the strength from his legs.

"I fell ill 10 days ago," Pogacar told a press conference in Florence.

"I had Covid and there was a little question mark but I am fully recovered. It wasn't so bad. It was just a cold that passed quite quickly.

"Covid is no longer as virulent, especially if you've had the virus before. I've already had it once, maybe twice even, I don't remember."

The 25-year-old fell ill during a training camp at Isola 2000, a ski resort in the southern French Alps.

His otherwise "perfect" preparation was also upset by the death of his grandfather and the consequent return to Slovenia for the funeral.

Visma rider Vingegaard, 27, was not reading too much into the news of Pogacar's Covid.

"It depends if it was a bad dose," said the Dane. "I don't know how much it will take out of him, but it doesn't sound perfect."

The peloton and its Fab Four - Pogacar, Vingegaard, Roglic and Evenepoel - were given a rapturous reception by fans and curious tourists alike in front of the 800-year-old Palazzio Vecchio with its copy of the Michelangelo sculpture David.

Pogacar, after his heroics here in May, got the loudest cheers telling fans "I'm honoured to have superstars as teammates".

Former Vuelta and Giro champion veteran Roglic appeared the most relaxed of the four.

He arrived in the brand new 'Red Bull' outfit in black and red and a six-million-euro contract recently signed.

"Each of us is part of the story," said the 34-year-old winner of the warm-up race the Dauphine.

"Sometimes you win, sometimes not, you have to do your best possible.

"Life offers you opportunities and to try and win the Tour, I changed teams to be here, but in the end there's another one next year too if this goes wrong."

The Tour sets off Saturday for four days of racing in Italy with race director Christian Prudhomme promising a "brawl" from day one.

Roglic and Vingegaard tipped Mathieu van der Poel or Wout van Aert to take the overall leader's yellow jersey whilst still in Italy.

Van der Poel, 29, who has had stage wins in the 2021 Tour and the 2022 Giro, revealed his Alpecin-Deceuninck team had been doing their homework, with one eye on the Paris Olympics which follow the Tour.

"Our team have looked at nine stages," he said of how many times he or his sprinter teammate Jasper Pedersen could win.

"And I want to get into top shape for the Olympics right after that," he said.