The Celtics allowing the fewest points is kind of a misleading stat. Don't Get me wrong, they do play good defense, its just not the "great" defense that everybody seems to think it is. They actually win by outscoring their opponents, not with lockdown D. The reason they allow so few points is because they run a grind it out half court offense (which they are very effective at) that eats up chucks of the clock at a time. This allows fewer opportunities for the opposition to score. This really allows for fewer shot attempts by the opposition when the Celtics get an offensive rebound and use up another 17+ seconds off the clock.