The Callahan revisionism is the dumbest thing I read on Nebraska message boards.
-He was such a great HC that no team has interviewed him to be a HC since then.
-He was such a great HC that he went 5-7 in year 4.
-He was such a great HC that when he was fired, no one (fans, players, media, message boards, etc) was in his corner. It was unanimous.
You can be a good recruiter and be a terrible HC. Callahan proved that. He'd be a great OL coach but there is good reason why he was never given the keys to a program again.