Chatman plays a bigger role than most might expect and Emery will be more mercurial with his shooting and scoring contributions and won't have as big of an impact as some might expect. I think Chatman will fill that role that we saw Anson Winder play, sort of the glue in the guard rotation and he'll fill in some at the 1 and the 2. He might not be a huge scorer but will provide some very good depth (maybe 6-7 pts a game).
My second surprise will be that Cooper Ainge won't be as good a player as his father was. I know that will come as a shock to many and I'm sorry to be breaking that news to you but I think it's important to have realistic expectations here.
Third surprise is that Braiden Shaw is a better player than most of us thought (but due to depth at the 4-5 spot he will likely redshirt this year).