I dont have any inside knowledge, but my thoughts are this:
Pereiro might be a former TdF winner, but he knows that aside from 'roid landis getting the axe for cheating, he won because of a 30 minute breakaway gift on a transitional stage, and an admirable defense of the jersey. These guys are pros, they know that they have and havent got. I suspect OP knows Valv has a much greater potential to win a TdF than he does and understands his job is to shepherd him. Should Valverde get into trouble and have to abandon, which he's got a propensity for, Pereiro is ready to assume the leadership role.