I think it bears repeating just how bad things are right now. The Bulls were kind of a mess before this rash of injuries, but there's a long step down from 'inconsistent team that probably doesn't have enough' to 'good god my eyes and ears' level we've seen lately.
The Bulls defense started out quite well this year, posting a top-5 ranking even though it didn't always look good. Perhaps between the intrinsic habits forged by Thibs and a quality defensive-minded assistant coach in Jim Boylen would hold things together. But then the Bulls defense started to suffer when Joakim Noah was hurt (then hurt again), and now with Jimmy Butler and Nikola Mirotic out for weeks it could get really bad.
The Bulls are now 11th in the league overall this season, but even if you include the 20 minutes Butler played in Denver, it's been awful the past 5 games. Worst-in-the-league awful.
Ironically, the opponents turnovers have actually gone up a bit, perhaps due to E'Twaun Moore getting a larger role and Mike Dunleavy returning. Or it's just a real small sample, which hangs over this whole thing.
Without Noah, it means more Gasol (and Gibson, which appears to be breaking him too). Without Mirotic, it means more Portis (Mirotic is passable, whereas Portis is truly awful defensively, though he gets somewhat of a pass being a rookie) and Bairstow (gets no similar pass, except a boarding pass to a D-League city). Without Butler, it means more McDermott, Brooks, and Tony Snell, who is ok individually but a poor team defender.
This isn't a blip, the Bulls will be without those guys for weeks (and obviously Noah for longer). The Hawks are somewhat uniquely good offensively (check this out, this is Hoiball), but man did things look really rough in that game. I pointed my cell phone at my TV for a minute for these, so they should be seen, it's evidence of a team trying to mask bad individual defenders by switching, but it just gets them cross-matched or non-matched due to poor habits.
And another issue is that even when healthy, we could see cracks in the defensive facade, and know that Fred Hoiberg is not a coach who cares as much about defense as he does offense. Boylen undoubtedly helps, but as Taj Gibson mentioned last game: the Bulls used to sustain injuries before and use their team defense as 'more than enough' to get some wins. This doesn't look like a team that can overcome injury to win games.