I think you are greatly underestimating what a new center, coming into a a new blocking scheme, with different protection calls, and an entire line that is unfamiliar with each other would entail if you are refering specifically to the Dolphins.
McD has already spoken about the importance of cadence, and it's nuances. I'm not as high on Tretter as most here to begin with, but regardless of who is anchoring that position, I want him taking a majority of the snaps fro day 1 of minicamp.
It's fine if ppl don't think it is important because he is a veteran, but i think it is incredibly foolish to dismiss the need for the linemen, and center in particular, to work together as much as possible before opening day.