Timelord as free safety should shore up some of our defensive woes, but the offensive wrinkles certainly require more effort and active thinking so it's not unreasonable to see the defense suffer a little in early days.
If you think of the big change over the last season, RWill is out and we have added Brogdon. A lot of defense out, a lot of offense in. In that context, it is not surprising that our defense has slipped and our offense has improved. I think that is the simple, obvious explanation.
More generally though, we just lack size and athleticism in our big rotation. Horford is a year older. RWill is out. Grant plays good on ball defense but isn't that kind of "have your back" big defender that allows tighter perimeter defense. Vonleh and Kornet, well, enough said.
But somehow, we have been able to start the season 11-3. RWill will help for sure. And we probably do need another reliable experienced big. We are fine though and Mazzulla appears to be a perfectly capable coach, maybe better than "capable". We'll see.