Jeff Green's ceiling: Lower than Rondo with a jumpshot, higher than Glen Davis with a vertical.
Okay, now that I've said my cutsey phrase..
I see think Jeff Green's career path could in a lot of ways mirror Jason Richardson's...if Richardson were a 3/4 instead of a 2/3. I'm not sure that makes sense..but stay with me.
He's athletic, but not so freakishly athletic that he can rely on it to dominant. He could be a second option on a poor to mediocre team with a little more consistency and focus in his development. But, if he can find a niche he could be a viable rotation player by around say 27 on a legitimate contending squad. He'd need to learn the 3 though, and would only play in the 4 in strategic situations, as opposed to out of necessity like he did in OKC...and his shooting needs to improve to be a real 3.