There seems to be little disagreement that the Celtics defense needs to improve. There also seems to be a general agreement that the Celts need another big man to help protect the paint. Where there is little agreement is which big man is the right one and how exactly will he, whoever it might be will improve the defense.
If we take a step back, the real issue is not defense alone, but rather the differential between offense and defense. If the offense scored more points on average, then the current level of defense would actually be fine. To put it in raw numbers, the Celts currently average 95.9 points per game. But they are allowing an average of 97.4 points per game for a differential of -1.5 points. Obviously allowing more than you score is a recipe for disaster.
It is really the differential that matters most. To put this into perspective, in the championship year of 08-09 the defense averaged allowing 93.4 points per game, not a whole lot better than now. But the team scored an average of 100.9 points per game for a differential of +7.5. In 09-10 - off. 99.2/ def. 95.6/ diff. +3.6. In 10-11 - off. 96.5/ def. 91.1/ diff. +5.4 ( two seasons derailed by knee injuries to KG and Perk). And last year when we fell one game short, off. 91.8/ def. 89.3/ diff. +2.5. It would appear that around +5 differential is the minimum level of differential to make this team a true contender for the title.
Considering that we are currently allowing an average of 97.4 points, the offense would need to improve to an average of 102 - 103 points per game. With the best being the championship year at only 100.9 I would think this is unlikely. Conversely, since we only average scoring 95.9 points, the defense would need to tighten up to allow 90 - 91. Last year's mark was 89.3 so this is doable. Doc clearly recognizes this as his various comments such as "make or miss league" and "we don't score a lot of points so we need to get stops" shows. But how?
Jeff titled one of his recent posts "No Glaring Weakness on Defense." And it is true, it is hidden. If you go to Synergy Sports and look at the offensive and defensive points per play, no single player including those who are receiving the most wrath are not posting respectable to very good numbers. The problem is they are not translating into good team defense. And there is a reason for this. Using a chart (courtesy 82games.com) it is all about shot clock usage.
Shot Clock Usage
Where the defense is getting killed is in the first ten seconds of the shot clock. Much of this is transition, but what it shows is that the defense is actually almost 100% better from 11 - 20 seconds (when it has time to get set) and even better yet with the shot clock winding down. (Notice too that the offense is better the earlier in a possession). This is why in the sideline interview early in the Clippers game Doc said "we want to run., we don't want them to run." Here again, Rivers has a clear grasp of the issues.
This is why Bradley matters. Assuming that he comes back at anywhere near the level he was last year, his on ball defensive pressure buys time for the rest of our team to get back and get set into their defensive schemes where they excel. He changes the dynamics and helps to tilt the odds in our favor of getting the team defense back to where it needs to be. Plus it frees Rondo from expending so much energy on defense that he can go back to being the all around disruptive force that we need him to be.
I think that the thought that Bradley will be the savior of the Celtics' season is over the top, but it is also hard to deny that he is an integral piece to the puzzle. It is also why I think that any deal that would include him for anybody is off base and should be off the table. His return, (and again I must stress at anywhere near his previous level) may not make getting another big unnecessary, but it could well make it less critical. And he could well change the choice of who and what skills they possess should be.
We will know soon enough. January 2 is Wednesday.
(Note: points in the chart do not add up to the averages with the difference being foul shots when the clock is stopped.)