A blocking specialist, Hartsock surprisingly graded out as one of the NFL's top tight ends in PFF's 2013 rankings.
Now he's a member of the New England Patriots, who added Hartsock and two other tight ends to the roster on Sunday.
Miller followed Gronkowski as the University of Arizona's tight end from 2009-13.
The Patriots clearly were unhappy with their depth behind Gronk, waiving two tight ends before adding three more. Of the players signed today, Hartsock is the most likely to make the 53-man roster.