Per 48 or per 36 minute stats are really only good to measure and compare the rate of production for a player. It really doesn't tell you if a player will be that productive if his minutes are stretched out to 36.
Sullinger shows all the signs of becoming a solid rotation guy, at least. He has real good basketball instincts, a good shooting touch, and a natural ability to get his shot off over bigger guys.
What I'd like to see is the Celtics dump the ball to Sully in the low post against similar sizes or smaller covers, and also step out and drive against bigger guys. The Cs desperately need inside scoring, and Sully's their best bet right now.