Five decisive Tour de France stages

► Stage 4, July 7: Seraing-Cambrai, 223.5km

After the drama and excitement of 2014's cobbled stage, organisers decided they could not do without them this year. Although there are slightly fewer sections and less overall distance on the cobbles (seven sections and 13.3km compared to nine and 15.4km), they come on the longest stage of the race. And the three previous days will have already provided possible time gaps to be created on the opening timetrial, the potentially windy second stage or the third stage's finish on the brutal Mur (wall) de Huy. Anyone already struggling or haemorrhaging time before hitting the cobbles would be under pressure and at risk of falling out of contention. A crash on the cobbles can result in the loss of several minutes

► Stage 9, July 12: Vannes-Plumelec, 28km team timetrial

This team race against the clock is not particularly long but the problem comes from the potential to reach it without a full compliment of teammates. The potential perils on the eight previous stages, including crosswinds, cobbles and the inevitable crashes, mean some contenders might arrive at the team timetrial without a full nine-man team. A team not set up with powerful rouleurs built for timetrialling, that had already lost a couple of riders, would likely lose considerable time

► Stage 10, July 14: Tarbes-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 don't react well to having their race routine broken up by a rest day. Anyone who needs a couple of days to find their legs again would risk paying dearly on the hors-category finish to La Pierre-Saint-Martin. It's not particularly long so the pace could be high leading into the final climb, meaning anyone having a bad day would be in for a torturous final ascent to the finish

► Stage 17, July 22: Digne-les-Bains-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. The first is stage 11 with a long descent off the Col du Tourmalet before a short third-category climb to the finish. This one has a fast, technical descent off the first-category Col d'Allos before a sharp second-category ride to the line. It's a similar stage to the one at the Criterium du Dauphine where a daring attack from Nibali allowed him to put time into the likes of Froome. The problem is the final climb is so short that there is little chance to make up time lost on the descent. If the weather is bad on top of that, a tentative descent of the Col d'Allos could be costly

► Stage 20, July 25: Modane Valfrejus-Alpe d'Huez, 110.5km

This isn't as tough a mountain stage as the previous day's with more climbs to crest but it will be the last-chance saloon. The second-last stage's finish on Alpe d'Huez - having already climbed the Col de la Croix de Fer on a relatively short and punchy 110.5km stage - will give riders one last hope to make a difference. As it's short, the pace should be high and there is no flat section. As it's the last chance to gain time before riding into Paris, the challengers to the overall leader will be forced to give it everything. And the likes of Nibali, Froome and Contador certainly aren't going to settle for consolidating a podium position. Those not in yellow will attack and that could mean fireworks