Chris Froome believes the Tour de France can work without spectators - but questioned how organisers can prevent large crowds converging along the course.
Initially due to start on June 27, the coronavirus pandemic has seen the Tour pushed back until August 29 and doubts remain given the differing Covid-19 situations across the world.
The French government says no mass gatherings can take place before September, but have clarified the Tour could still go ahead on its new dates if the opening stages are managed correctly.
That is one of the main things four-time champion Froome believes will be hard to govern as he continues to prepare for a tilt at another victory.
"For sure we can put the race on without people standing on the roads and fans in that sense," the Team Ineos rider said.
"I mean, we can put on the race and it can be broadcast on television.
"You're not going to get the same scenes as you would get going through these tunnels of just people everywhere and all the rest of it.
"Maybe that's the version of race we need to see this year. I don't know.
"In theory, we can put the race on but I think the bigger question is would the organisers be able to keep people from actually coming out and gathering in large crowds? I think that's the bigger question."
The 34-year-old missed last year's race after suffering career-threatening injuries in a crash.
And Froome has been hitting the gym first thing every day to try and replicate what he would be doing this time of the year in preparation for the Tour.
"Some days I'm even doing up to six hours sitting on the stationary trainer - big days," he told former cricketer Kevin Pietersen on an Instagram Live.
"It gets pretty boring at times. I've been through every playlist I own about 10 times each.
"But, yeah, just getting through it and doing the best I can.
"Obviously I'm coming off the back of a big injury now as well.
"I mean, a lot of the training I've been doing up until this point has been indoors already, so it's almost prepared me in a way for this whole lockdown period and I think mentally I'm obviously able to get through it a bit easier."
For the next five days, riders from a number of professional men's and women's teams will compete in online races as part of a month-long charity fundraising initiative open to the public on Zwift's virtual platform.
Line-ups will change daily as teams rotate their riders, but British duo Adam and Simon Yates are in Mitchelton-Scott's squad for the event, while British national champion Alice Barnes can expect to face former world champions Marianne Vos (CCC Liv) and Anna Van Der Breggen (Boels Dolmans) in the women's event.
Zwift will donate £100,000 to Doctors Without Borders/Medecins Sans Frontieres throughout the event, a sum which will be doubled if 250,000 people complete a stage.
For Canyon-SRAM rider Barnes, the race offers some welcome competition as she awaits tomorrow's planned UCI announcement on when WorldTour racing might be able to resume.
"Zwift races are really important not only to maintain some focus and racing intensity but also for exposure for the team," Barnes said.
"I would love to be racing and I am missing the adrenaline of being in the bunch but I am grateful for my situation. I think at the moment there are a lot worse problems in the world than our sport.
"We will have to wait for when the time is right to get racing again and make sure that we are ready for it."
The racing will be broadcast live via the Global Cycling Network and Eurosport, with the women's races taking place ahead of the men's.
Today's opening stage will be a 52.9km test on a virtual edition of the Innsbruck circuit used in the 2018 Road World Championships - which is when Van Der Breggen claimed the rainbow stripes.