1. Riley
2. Callahan/Bo tied, equally crappy for some of the same and different reasons
3. Solich
I'm not defending Callahan, but look at it objectively. He took over a program that had totally gone to a QB run heavy offense the two years prior. He inherited Joe Dailey. Yes he went 5-6 his first year attempting to transition to his offense. Pretty much blew the Southern Miss game with turnovers, which could have meant a winning season.
2nd year, he gets Zac Taylor. 8-4 record. Lost to TT at TT by 3. Lost to OU at home, by 7, a bad loss to Kansas at Kansas when Mangino was starting to turn them into a very good program, and a loss by 14 at Missouri. They have one of them more enjoyable victories in the last 20 years at Boulder that year (unexpected 30-3 victory), and topped it off with a win against Michigan in the Alamo Bowl (yes there was some officiating issues in that game). TT ended up # 20, OU # 22, and Nebraska # 24.
3rd year, division champions, lost to OU in the CCG. Lost a close game in the Cotton.
4th year, high hopes, Game Day comes to town because people actually thought there was a chance against vaunted USC. IMHO, this is when we saw just how much Adam Carriker and Jay Moore covered for Cosgrove's flaws as a DC. They left and the D went to hell.
So in 2 years, he completely changed the offense and gets Nebraska to the CCG. I don't care what you think, that was an amazing accomplishment.
I've said it before, but had BC done two things in 2007, who knows what might have happened. 1, start Joe Ganz and 2, get just an average DC in place of his buddy, and he just might still be here.
Now take Pelini. The guy could coach without a doubt, when he had great players. That 2009 Gator Bowl was awesome, and 2010 he had just an ungodly defense. But the guy didn't seem to want to do the things that a HC needed to do in order to maintain success.
I like to compare Bo and BC after 3 years, because in year four, Carriker and Moore were gone as I mentioned, and in year 4 Bo was starting to run out of Callahan recruits. In years 1-3, BC was 4-6 vs ranked teams at the time they played. Bo in that same time was 5-7. In their careers at Nebraska, BC was 4-10 (40%) vs teams ranked when they played, Bo was 10-15 (40%). Pretty equal crap.