I dont think he is necessarily ready yet either, but he has to be better than Chad Durbin. Also, being allowed to start off in the #5 spot should do a good bit to relieve the pressure on him to come out and dominate right away. Cole Hamels was brought up early last year as well, and he has done well so far.
Despite him being a former Tarheel, I think that Miller is going to turn out to be the sleeper of this year's pitching class. He knows how to win, and is used to fighting through on a pressure filled stage. We will see what happens tomorrow.