Hawkwood said:
How do you know this, has Contador ever ridden clean so that we can know his undoped ability?
I don't know this, that's why I said, "IMO".
It's a wild guess. In order to make a better guess, I'd need to know who, if anyone in the GC, is riding clean.
Then, from there, I'd know who the best clean rider is.
And, from there, I could guess how much each of the superior riders is doping, and try to discount that from his ability.
That's a lot of iffs-and-buts. So, as I said, "IMO".
However, there are a couple of things in Contador's favour compared to Froome: style on the bike, size, good from an early age...