I skimmed the replies to see if this was here. If it hadn't been, it's the topic I would have touched.
It was "easier" for Manny to recruit a Lashlee because the negotiation is straightforward: "hey, wanna basically do whatever the **** you want, take the world's worst offense, transform it, and flip it into a Head Coaching gig in the near term?"
The one for a defensive coach will be far more complicated. First, will a badass DC feel Diaz has enough juice? In short, will he respect him enough? Will the philosophies match? As a former DC, will Diaz be ok allowing a DC the same type of autonomy he's given Lashlee?
Something has to happen with the defense. Specifically, the playcalling. Think this is a good topic for discussion because my guess is Diaz sticks with most of his crew. I mean, it's straight up his defense.