Dear Wiggo said:
Let me put it to you, seeing as I am on one side of the fence and you are perched precariously on it: if Wiggins podiumed in 2 or more GTs this year, would you say that is normal?
Giro-Tour would be unusual, given the time gap between the two is too long to hold a peak and too short to recover and re-peak with plenty of riders aiming to peak at one or the other. Exhibit A = Berto 2011.
Giro-Vuelta seems entirely plausible if a rider is good enough to podium in a GT, as there's enough time to recover and re-peak. Exhibit B = Berto 2008.
Tour-Vuelta would be similar to Giro-Tour. Exhibit C = Froome 2012.
However, this is all old ground. I've said plenty of times that I think Sky/Wiggo are suspicious. My particular point this time round was that however you try and spin it, Wiggo's opposition last year (particularly in the Tour) was weak.
If you don't believe this, draw up a list of riders who had demonstrated GT podium form in recent seasons. This seems like a decent proxy for "quality of rider" when assessing a GT field. Then see how many of them rode the Tour without the obvious handicap of a hard Giro in their legs. One list is much shorter than the other!