Imo it's not Contador that's become worse, it's his aggressive racing style, which nowadays is totally ineffective. He's facing a much stiffer competition than in the last few years, so he needs to be more conservative. In the Vuelta he was lucky he was racing against competition who had their bad days as well, Froome on the other hand can rely on an alien recovery system. If Contador goes berserk on each Tour MTF this year, Froome will turn on the diesel, close the gap and leave him behind. Anyway, tires will be smoking this summer...