It is getting better on the side of the ball where the Celtics make their living as a team.
C's defensive improvement in focus - Boston Celtics Blog - ESPN Boston
In case you are wondering, the Celtics lead the league in opponent points, opponent field goal percentage, and forced turnovers during this three-game stretch. Hang around the top five in those categories for a while and a team will enjoy a tremendous amount of success.
The least surprising thing ever is the fact that the Celtics defense improved when Avery Bradley returned. But it is impressive that it has gotten THAT much better.