Gung Ho Gun said:
Contador won both Giro and Vuelta in 2008, and Nibali would have done the same thing in 2013 if it wasn't for Horner
Huge difference between winning the Giro-Vuelta double and winning the Giro-Tour or the Tour-Vuelta.
Firstly, the recovery period gets slashed in half. After a three week race any normal human being needs a period of rest before they can get back into top form. Managing to both fully rest and get back into Grand Tour-winning form is almost impossible in the short time between two consecutive tours.
Secondly, the competition in the Tour is usually much harder, so winning it takes more from the rider.
If Froome wins four consecutive Grand Tours
it will be the biggest raised middle finger to clean sport I've ever seen.