I'd argue Pendergast could be blamed for AZ's loss at the superbowl last year. he's proven he's mediocre...but maybe he'll get lucky w/ the Chiefs. This is cronyism at its finest IMHO but I digress.
****maybe defensive coaching is more about the players and less about the coaching.****
off the top of my head...
Romeo - supposedly good DC but team was fine without him.
Marvin Lewis (good DC, then head coach that couldn't spell D)..and the Ravens were fine without him.
Buddy Ryan...got a lot of credit but had great players
Gunther - was a genius when he had DT and Neil and decent cast down in Tenn. but otherwise pretty average.
the list goes on...
maybe defensive coaching doesn't matter.