For the first month of this season, the Celtics held the #1 slot for Defensive Rating in the League. They were allowing only 101.0 points per game as of November 15, 2018. Since that date they have fallen to 10th place, allowing 107.1 PPG. Can this be the main cause of their up-and-down season?
In answer to my own question - you can bet the drop in defense has been part of the reason the Celtics have been under-performing expectations.