He looked brutal last night and one big reason why imo has to do with added weight.
He definitely looks 10-12 pounds bulkier but it is also affecting his agility, quickness and ability to jump quickly off the ground. Just "sluggish" out there. Two instances where he let a few sg/sfs guys get layups around him. Before he could react/jump, the ball was already in (since he doesn't have exceptional length, he needs to be able to jump quickly off the ground for these kind of situations). On the offensive end during a few PNR plays , he couldn't get to an open spot quick enough. By the time he was ready to shoot, there was a guy all over him. This happened several times (something that rarely did last season).
He has to lose 5-10 pounds. Not be as skinny as last season but not as bulky as he is now. Somewhere in between. He has to get his quickness, athleticism, running ability back.
On another note, i'm disappointed with Sullinger. The guy has not improved his shape/condition to the level it should be after having a full offseason this time. Look at KO in comparison. Come on Sully