I guess the more I think about this the more it kind of clearly is Lawson as the most disappointing player. It is a larger fall from possible all-star to out of rotation than from rising prospect to complete bust (Stauskas , Bennett), or from starter to bench (Pierce) or From MVP to all star (Davis).
A few people have said Harden. He has had some curious games (he basically refused to shoot in the loss against the Nets), but in general he has seemed like is playing hard in the games I have seen. It seems like either the overall chemistry is toxic, they really need josh smith back for their second unit, or they have already started to turn it around with their frontcourt getting healthy (montejunas and Jones now playing).