By Julien Pretot LE LIORAN, France (Reuters) - Italian Vincenzo Nibali started the Tour de France looking to assess his form after a grueling Giro d'Italia and he came up with a tough answer on Wednesday -- he is not quite there yet. The 2014 Tour champion has been tasked with helping his young compatriot Fabio Aru, but he was not even able to do that during the fifth stage, cracking in one of the short but tough climbs of the day in the Massif Central. Nibali's coach Paolo Slongo hinted on Tuesday that his rider could make his own move at some point if he had the legs. More...