Not necessarily advocating for his return, and that is for the very resons you point out: The Fangio D isn't the surprise that it once was. That he didn't turn Joey Bosa, Khalil Mack and Derwin James into at least a middle of the pack defense says something
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I was only pointing out that as long as Staley is available, we'll always have a fall back. He knows the base defense we've been playing for years, he knows how to work with McVay. maybe if he's concentrating on just being a coordinator and not a HC he'll refind his magic.
Can we do better, possibly. Can we do worse, probably.