Jaylen Brown is really the wild card here. His improvement from year-one to year-two was remarkable, and the best part is that he did it out of necessity. The team needed that improvement from him when he was given the extra floor time.
But we can not put a finger on exactly how good Brown can be. In my interview, Brian Scalabrine compared portions of Jaylen's game to what we saw from Michael Jordan. Scal was not saying that Brown was the equal of Jordan, nor that he would become that.