AJ Smith.  The talent level has come way down.  Since he's lost Buddy Nix (the only person who could tell him 'no') he has had some horrible drafts.  And then there's his horrible "I am the boss and am always right" attitude that has pushed out guys like Cromartie, Vincent Jackson and Darren Sproles.  He was so full of himself he thought he could replace them.  He didn't and hasn't.  The O-line is horrible (you and I could get sacks on them), turning Rivers into David Carr lite.  There are no weapons on offense that scare the other teams, and the defense can't muster a consistent pass rush.  
Norv isn't the world's greatest coach, but you have to look at what he has to to work with.  The talent is not there, at all; but the expectations are still there because they have a decent QB and memories of that 14-2 season.  A team that was loaded with All-Pro talent and "best at their position" players just a few years ago is now merely average - and that's not coaching - it's an egotistical GM who thinks he's the greatest thing since sliced bread.