Last year the defensive secondary of Sean Smith, David Amerson, Reggie Nelson, and Karl Joseph (as well as DJ Hayden and TJ Carrie and some other fill-ins) had a very up-and-down year. They made some key plays but many of those were overshadowed with some egregiously poor plays, many of those stemming from lack of communication. It wasn't necessarily that they were PHYSICALLY bad, but that one or more were just out of position and not quite sure where his help would be or was supposed to be.
This offseason, somehow GM Reggie McKenzie and HC Jack del Rio pulled off a major coup by getting veteran defensive coordinator John Pagano to ASSIST Ken Norton in handling the defense, while primarily working with the aforementioned defensive secondary.