LYON, France − On the lunar landscape of Mont Ventoux, Chris Froome faces the toughest threat yet to his Tour de France lead with his rivals − sensing vulnerability in the Briton’s Team Sky − set to go for the jugular on the imposing ascent Sunday.

Froome has never climbed the Ventoux, a 20.8-km uphill drag at an average gradient of 7.5 percent, in race conditions.

“It’s a climb that is different from others. The truth is that it is extremely hard in the first part. In 2009 at the Dauphine, I had the feeling I was puking my heart out. Then on the Tour a month later I was more in control,” two-time winner Alberto Contador told reporters.

Contador sits in third place overall, 2:45 behind Froome, with second-placed Bauke Mollema of the Netherlands 2:28 off the pace.

Froome lost 1:09 to the pair on the 13th stage after being caught off guard by a brutal acceleration from Contador’s Saxo-Tinkoff team.

His team’s weaknesses were exposed on Friday and during last Sunday’s second Pyrenean stage, when Sky was blown apart following Garmin-Sharp and Movistar’s early onslaught.

Although Froome has not looked in serious danger so far in the climbs, he found himself isolated in the second Pyrenean stage. Should this happen again today − the longest stage at 242.5-km − there is no guarantee that the Briton, who has shown signs of nerves in the last couple of days, will not crack.

"[Sunday] is the day where there is a lot of people who have a lot of interest in the race because there is going to be two races − the breakaway can go to the line and someone can win the Mont Ventoux stage, and then there’s going to be a GC [general classification] race,” said Garmin-Sharp sports director Charly Wegelius.

Just like in the Pyrenees, Garmin-Sharp could be the team to shake things up, with Americans Tom Danielson and Andrew Talansky, as well as Irishman Dan Martin, using their collective force to cause chaos − their strategy going into the Tour.

“We’re obviously happy with how things are and we’re taking it one stage at a time, but fundamentally our overall view of the race did not change,” said Wegelius.

The wind, however, could play a big part in the scenario.

“There are two parts in this climb,” said Contador, whose never-say-die attitude has been keeping Froome on his toes despite the Briton’s fine win in the first mountain stage in the Pyrenees.

“The first one [in the shade] is so steep you feel like you’re stuck on the road. Then in the last five kilometers, you usually have wind and often it’s headwind, so it’s best to sit behind someone else’s wheel in that part.”

Contador, not a rider who races for second, is likely to try his luck, as will the Movistar team, which missed the death blow in the Pyrenees after failing to attack in the final climb when Froome was left with no teammate.

Their team leader, Alejandro Valverde, fell out of contention on Friday, but the Spaniard has promised fireworks, while Colombian climber Nairo Quintana, who is looking to secure at least the young rider’s white jersey, is unlikely to stay quiet.