He was successful with Carrol's players and scheme, just like Richards and Gus Bradley. They've all been flops elsewhere and all have had middling defenses at best. That is Carrol's defense. The legion of boom was because of Carrol. He is one of the most gifted secondary coaches ever. Until one of these guys leaves and has success elsewhere, I won't give them credit while working under him.
I thought Edwards would be the natural choice, but I also don't get paid to do this so it's not my responsibility to scout coaches. I also really like the DC for thr Bearcats, but he's probably too green. If you want to pay me what an NFL GM makes I'm sure I could produce an extensive list of coaches I would have preferred.
Quinn did have some success elsewhere. His Atlanta team was 11-5 and went to the Super Bowl his second season. It was 10-6 the next year, when the defense was eighth in points allowed, holding five opponents to fewer than 20 points during the regular season and both of its opponents in the playoffs to 15 or fewer (26-13 over the Rams and 15-10 loss to the Eagles).
Imagine if we had a defense that held any opponent to even 17 points or fewer in the playoffs during some of the years when our offense was actually good. Even in the 2016 playoffs, when his defense wasn't as good and gave up the big Super Bowl comeback to New England, it held its two NFC playoff opponents to 20 and 21.
Now, the last three years haven't been good defensively, so there is some concern there.