Couple of issues, but I am with you in spirit.
1) The roster is full. Do we have anyone eligible for the D-League? If not, someone has to be cut.
2) At the very least, VERY LEAST, we can give him Scal's minutes and it will be an upgrade. There is no argument that he has the talent to contribute.
3) Player development. My hope is that Ainge has him down there to learn / refine a few specific skills at game speed. If he came up now, his minutes would be limitted and his looks would be non-existant.