My bet is Garmin.
They managed to win it in 2011 with Vande Velde, Hesjedal and Danielson as only clibmers in the team.
I feel in 2013 Hesjedal is stronger than then, Danielson is around as strong (he had perhaps his best spring ever, including 4th place in Romandie- his best ever place in WT), and while Vande Velde may not be as strong, there are also Martin and Talansky in the team, so they have far more depth than then and with the aggresive strategy they are supposed to have for this race, things are looking good for some breakaways for them, what should be important as well.