Not 100% certain he is coming out but if he does Willie Cauley-Stein might slip to the Celtics. If he did, that's the big guy I draft. Unreal athlete(he played wide receiver in high school football) for his size(a real 7'0" and 245 lbs of muscle), Cauley-Stein is a major project offensively but has giant upside defensively with some of that coming almost immediately.
I think if he could learn the system fast enough, Cauley-Stein could be giving this team rotation worthy minutes before the end of next year. He would be the rim protector, weak side shot blocker, defensive inside anchor that this team could build around long term, well, along with Rondo, Sully, Bradley and Green, that is. And if he ever untaps his potential as a low post offensive threat, watch out. He could be a star. His athleticism is that good. He runs so naturally, like a sprinter and has good hands and can finish noisily on the break.
My secret desire is that Danny trades up and drafts Nerlens Noel but other than that, I would want Cauley-Stein. He would fit perfectly if he develops as some project. Is he a project? Yes. But I think a more sure bet to invest in than Fab Melo with much much higher upside.
Then again, he would have to fall some for the C's to land him at this point. He's probably gone by 15 or so.