Good additional info JR4AU, but don't forget that USC had kind of a "perfect storm" last year as far as how all their talent played out. A lot of guys red-shirt, get hurt, transfer, or leave early for the NFL.
All of those factors contributed to them losing nearly their entire defense to the NFL after the 2008 season. No matter the talent, it's hard to have so many new players all at the same time....along with a freshman QB (which was due to losing their old one a year early to the NFL).
It's similar to how Florida went 13-1 in 2006, then 9-4 in 2007, then 13-1 again in 2008. They had just as much, or more talent in 2007, it was all just young and without as much leadership.
It would have been interesting to see what Carroll would have done in 2010, to see if he bounced back or not. History says he probably would have. Will see how dick head does.