Hard to see past Froome, but hopefully Porte will make a race of it. My outside bet would be Bardet. He is improving all the time and has looked not bad so far this season.
Difficult to know about Quintana. Was he really ill at the Giro was was that his default excuse mechanism kicking in.
Nibbles and Bertie are too old now. Would like to see Bertie go out in style at the Vuelta rather than struggle in the Tour.
Could be a good year for Yates, especially if his brother recovers from the Giro and rides as his main support.
As for G, I still think his future lies in the one day Classics, but Sky and himself obviously want to try out over three weeks, and to be fair they know far, far more than any of us about his potential.