Vincenzo Nibali is preparing himself for the inevitable attacks he will face once the Tour de France reaches the Vosges.

Once Friday's mammoth, but almost entirely flat 234.5km stage from Epernay to Nancy is behind them, Nibali's rivals will start eyeing the bumpy Vosges stages and look for the the chance, perhaps, to snatch back some valuable seconds on the race leader.

As soon as Saturday's 161km run from Tomblaine to Gerardmer reaches its bumpy finish, that's where the attacks are likely to come.

With a complicated and chaotic first week behind them, Nibali is sitting pretty on a lead of more than two minutes on almost all his GC rivals.

And wearing the yellow jersey has been a blessing for the 29-year-old Sicilian, who rides for Astana.

"For sure the jersey gives me great energy but at the moment I'm just trying to ride in the best way I can. The yellow jersey is something extra," he said.

"For the climbing stages this could be an advantage in terms of the management of stage after stage. We'll see, I'm calm because fortunately the stages have gone very well.

"(Thursday) there were also a lot of crashes and you only need someone to slip in front of you and you could crash, like what happened to Chris (Froome).

"I'm sorry he had to abandon the Tour. There are things that scare you, like your rivals but I still have a good advantage and I must defend it and, if possible, take more time."

Although it won't have been ear-marked as one of the stages to gain considerable time, the succession of two second category climbs followed by a short but brutal third category (1.8km at 10.3 percent) ascent to the finish of Saturday's stage eight will encourage the likes of Alberto Contador to attack.

The last 26km include around 12km of climbing after 135km of pancake flat terrain.

Contador is 18th at 2min 37sec and needs to gain seconds wherever he can.

That's not likely to happen on Friday's stage seven, though, as the epic stage is mostly flat, despite two little fourth category climbs right at the end.

Depending on the various teams' tactics, that could result in the top sprinters being distanced on the tough 1.3km final ascent that has an average 7.9 percent gradient.

Thereafter there are only 5.5km to go downhill to the finish line so it likely wouldn't be enough to claw back anything more than a handful of seconds.

If the likes of Marcel Kittel, with three stage wins already this Tour, or Thursday's sixth stage winner Andre Greipel don't make it over that bump with the leaders, then the stage could be set for green jersey wearer Peter Sagan.

The Slovak has been the most consistent performer this Tour, finishing second twice, fourth three times and fifth once in the six stages, yet he hasn't won one yet.

If the main sprint competition is distanced, this could be his big opportunity.

"If I look back to the stages we've done, I have two different feelings. I have a good advantage in the green points classification, I finished always in the front," said Sagan.

"On the other side, this is not my first Tour de France, it's the third experience, and my aim is to do better and improve year by year.

"I had the chance to take the yellow jersey and I always get close to winning. Even (Thursday) I wanted to sprint but I had no luck.

"It's a little frustrating, maybe sometimes I ask too much to myself. But now I just want to keep concentrated and to try again."