I think a lot of his issues come from switching from mainly playing 3 to mainly playing 4. So he has to work harder on both ends of the floor because he is matched up against bigger, stronger players and it’s taking its toll. His 3-pt shooting percentage last year steadily declined from 39% in Q1 to only 29% in Q4.
It really looks like his shooting is affected by fatigue. Not sure what Boston can do to alleviate this, they are pretty much locked into a smallish White/Holiday/Brown/Tatum/Porzingis for the foreseeable future.
Clearly we have to look at the last preseason to compare results. Last preseason they were 2-4 with a -6.7 point differential, this season they are 1-3 so far with a -7.5 point differential. Seasons before that, 1-5 with -16.3, and 0-6 with -15.
There is a definite trend here, the worse they do in the preseason the better the team does during regular season. By that metric JJ is an improvement over Ham.