Not every player who is projected to get taken high in fantasy football drafts is going to have a good season. That's the way it works every year. Sure, many will live up to their potential and put up big numbers, but there are going to be some busts.
A player doesn't have to put up no points to be a fantasy bust. If you are expecting somebody to be among the top 10 at his position and he falls well short, that's a bust. Especially if it took you a high draft pick in order to acquire that player.