STAGE 4, JULY 7
Anyone already struggling or haemorrhaging time before hitting the cobbles (seven sections totalling 13.3km) would be under pressure and at risk of falling out of contention. A crash on the cobbled stones can result in the loss of several minutes.
STAGE 9, JULY 12
Vannes to Plumelec, 28km team time trial
This team race against the clock is not particularly long but the problem comes from the potential to reach it without a full complement of team-mates. A team not set up with powerful rouleurs built for time trialling that had already lost a couple of riders, would likely lose considerable time.
STAGE 10, JULY 14
Tarbes to La Pierre-Saint-Martin, 167km
This is not the toughest mountain stage but it is the first and it comes
straight after a rest day. That makes it tricky because some riders do not react well to having their routine broken up by a rest day.
STAGE 17, JULY 22
Digne-les-Bains to Pra Loup, 161km
This is one of two stages where a descent could prove decisive, and with Vincenzo Nibali and Alberto Contador superior descenders to Chris Froome or Nairo Quintana, those two stages could prove critical.
STAGE 20, JULY 25
Modane Valfrejus to Alpe d'Huez, 110.5km
This is not as tough a mountain stage as the previous day's with more climbs to crest but it will be the last-chance saloon. As it is the last chance to gain time before riding into Paris, the challengers to the overall leader will be forced to give it everything to make up for lost ground.