The Bulls offense has certainly seen it's ups and downs this season. When fully healthy (or when Rose goes bananas), the Bulls offense seems to perform admirably. However, with Thibs at the helm and plenty of solid defenders on the roster, it would seem that the Bulls defense would always be there to keep them in games. Lately, that has not seemed to be the case. I am starting to get the feeling that it is Luol Deng and not Joakim Noah or Taj or Asik that is the true defensive anchor to this team. To be honest, I am not 100% sure going in to this what the results will be, but it's an interesting topic to look at, and one that will weigh heavily on the success the Bulls might have in the future.
First, let's do the simple thing. Let's look at the Bulls defensive rating with and without Deng on the floor. According to 82games.com, the Bulls defense has been 6.5 points better with Luol Deng on the floor. While that seems pretty significant, you have to understand that part of this is due to the people backing up Deng. Korver, a less than stellar backup, will certainly make anyone's defense look better in comparison. Well, let's look at some lineup data instead. I took a look at some lineup data here. I tried to look at lineups that were identical in players other than Deng. Example 1, Rose/Brewer/Deng-Korver/Boozer/Noah. DRtg 95 with Deng, 100 without. So, Deng is worth 5 points on the defensive end over Korver. I hope this isn't something we are shocked by. Example 2, Rose/Hamilton/Deng-Brewer/Boozer/Noah. Here, Deng is replaced by Brewer, a more than capable defender. DRtg 107 with Deng, 95 without. Uh oh, what happened here? Well, for 1 the Bulls ORtg was a massive 116 with Deng in the lineup and 93 without (starting lineup is looking pretty good, damn injuries). My guess is there are two issues here. There is a large minutes discrepancy here. Big problem. Furthermore, this unit may have been running more, which could have caused issues on the defensive end. Plus, any unit with Boozer is just a mixed bag. Ok, now I have found the simple problem. We don't have enough data from this year alone. Well, let's look at some data from last year. Well, alas there is not enough comparable data there either. Brewer played too many minutes with Deng. We would simply be comparing Deng and Korver again.
FWIW, last year the Bulls defense was nearly identical with Deng on/off the court. Well, this is proving pretty fruitless. Let's try something a bit more simple. Bulls DRtgs in each game without Deng: 111.2,110.7,96.3, 102.5, 108.0, 105.3, 112.3. The Bulls DRtg on the year is 98.4. The Bulls have had one game better than that since Deng has been out. I am approximated the Bulls DRtg before Deng went out and got 95.5. Assuming I am close to right, the Bulls have had zero games where the did better than their DRtg for the season since Deng has gone out. To me, that's pretty persuasive, especially considering the fact that we didn't play a ton of offensive juggernauts in there.
Just from watching games, the Bulls defense has seemed awful without Deng. Even if he is a bit less proficient offensively, if Deng can come back and still lead the Bulls defense, he should give the Bulls a needed boost.