Updated

Chris Froome's grip on the Tour de France yellow jersey is expected to come under threat on stage 15, but team chief Dave Brailsford says Team Sky are ready for another epic day of racing Sunday.

Froome, the runner-up to teammate Bradley Wiggins last year, has led the race since capping an audacious attack 5km from the summit of Ax-Trois-Domaines in the Pyrenees with a stunning victory on stage eight.

The Kenyan-born Briton then stretched his lead further with a stunning performance in the 11th stage time trial, where he finished second to German Tony Martin.

But in between those feats, Froome has been given food for thought as rivals Alberto Contador, a former two-time champion, and Dutchman Bauke Mollema have come defiantly back into contention.

On Friday's 13th stage Contador's Saxo team initiated an attack which left Froome and his Sky team in tatters as they struggled to close the gap amid fierce crosswinds.

The Briton lost 1:09 to both Contador and Mollema, as well as the Dutchman's Belkin teammate Laurens ten Dam.

Froome still holds a 2:28 cushion over on Mollema, with Contador third overall at 2:45.

But the 242.5km-long 15th stage threatens to shake up the overall standings considerably: it is the longest of the race and ends with a 20.8km climb to the summit of Mont Ventoux where hundreds of thousands of fans are expected to line it's exposed and lunar-like slopes.

Sky may have shown chinks in their armour, but Brailsford was bullish when asked what tactics they would employ.

"We have no reason to be afraid of other teams at all," he said.

"Chris has already shown that he is climbing really well, time-trialling really well. He is in great shape and we are looking forward to it."

Events in recent days, however, have given Sky's rivals reason to believe.

The British team is minus two key riders in versatile Norwegian Edvald Boasson Hagen, who crashed out with a broken shoulder on Thursday, and Vasili Kiryienka, who missed the time cut last week.

The loss of both was felt immediately when Sky were unable to respond to Saxo's attack on Friday's wind-hit stage to Saint-Amand-Montrond.

And with other teams still chasing highly-coveted stage wins, their race strategies could favour Sky's rivals -- as shown by some aggressive racing last Sunday when Froome was sorely exposed and isolated on stage nine, won by Garmin's Dan Martin.

Garmin are without a yellow jersey contender but sports director Charly Wegelius believes Sky's recent setbacks show they could be there for the taking.

"It's given people confirmation, if they needed it, that Sky are not as strong as they were last year and they can be exploited," Wegelius told AFP on Saturday.

But how can the likes of Contador or Mollema hope to beat Froome after he showed his climbing class a week ago in the Pyrenees?

"Again, we need to have a situation where he's isolated and if the guy who is second overall (Mollema) attacks, we can't have the guy who is third overall (Contador) chasing him... and bringing Froome back (into the equation).

"He's still one of the strongest riders in the race but he lost a minute yesterday on a seemingly straightforward stage."

Scot David Millar of Garmin added: "If the others want to beat Froome, they have to beat him as a team. But they'd better do it before he gets on the climb.

"It's going to be horrible for everyone tomorrow. I'm sure it will be a fantastic race."

Contador underlined the difficulty of the climb and warned: "If you have a bad day on Ventoux you can lose minutes."

The Spaniard added: "Tomorrow I think there will be a lot of attacks. I just hope the legs work well."