Combined Minor League and Major League Plate Appearances is still under 1600 total. Prince had over 1900 PAs before getting called up, and Braun was only part way in to his second season with that same number of Plate Appearances. I don't know if Mitchell can radically change who he is at the plate, but it's still not hard to imagine there is a decent chance of a big break out now that he has been able to play for an extended stretch.