Five-time Tour de France rider Geraint Thomas has warned his fellow cyclists that wet weather may turn the cobbled fifth stage into a dangerous race.
Thomas, 28, is a key member of the Team Sky side trying to guide Chris Froome to a second successive Tour title.
|"You train all year for this and for it to end like that would be devastating for whoever it was"|
"On the cobbles it's sketchy anyway. If it does rain it could end somebody's race quite easily," said Thomas.
"You train all year for this and for it to end like that would be devastating for whoever it was.
"So hopefully it stays dry and everyone stays out of trouble."
Froome touched wheels in the peloton and fell just five kilometres into the 163.5km fourth stage between Le Touquet-Paris-Place and Lille Metropole.
The 29-year-old suffered a grazed left hip and wrist injury, before quickly getting back on his bike and rejoining the peloton, after receiving medical attention from the race doctor.
He is in seventh place overall, two seconds behind race leader Vincenzo Nibali after stage four was won by Marcel Kittel.
Wednesday's stage begins in the Belgian city of Ypres and ends 155.5km away in Arenberg-Porte du Hainaut.
Thomas helped Froome to the Tour title in 2013 in spite of suffering a fractured pelvis in a fall during the opening stage.
And the Welshman, who came second the last time he was involved in a race over cobbles, says it will be "stressful" supporting his team-mate.
"When you've got to look after somebody it's totally different to racing for it yourself," said Thomas.
"You can take a few risks, but you've always got to think of the guy behind you.
"But I think it's definitely a challenge - it's the same for everyone.
"So we'll just take it on and hopefully all will be well."