If Kelly starts from the beginning of the season and gets to play essentially until he fouls out each game (25-35 minutes), he could be a legitimate rookie of the year candidate by virtue of his scoring alone.
On this team, with top scoring options slated to be Jeff Green, Jeff Green, Jeff Green, Courtney Lee, Jared Sullinger, Jeff Green, Rajon Rondo, Brandon Bass, and Jeff Green, there should be plenty of room for Kelly to carve out a role taking 10-15 shots a night.