I have noticed more and more college teams utilizing the 4-2-5 with a third safety that can essentially move up to linebacker to form a 4-3, basically allowing a team to be ready to defend against any type of offense, especially a no huddle/hurry up offense. What I haven't seen is any team in the NFL consistently using someone interchangeably in such a fashion.
Taylor Mays always seemed like an ideal guy for that position in the NFL but his coverage skills were lacking, even for that. Brian Urlacher could have been the NFL prototype as he played safety in college and middle linebacker in the NFL, he certainly had the athleticism for both positions. I've always thought that its an interesting concept, if you watch teams like Auburn or TCU, they have an extra safety or two that can essentially do it, basically big strong safeties that are high quality tacklers, can read the offense and either move up or drop back depending on what the offense does and whether its a run or pass play, the defense is situated to stop it.
I remember the talk awhile ago that Seattle was going to move Kam Chancellor to linebacker but utilize him in the same "star" position fashion, move him back and forth between safety and linebacker depending on what the playcall was. The advantage of such a system is that you add a tremendous amount of speed to the defense, but still have that bigger bodied safety in there who can ably move up to linebacker and allow you to run 4-3 looks as well without having to substitute players in and out.
Karlos Williams, just like Nick Moody before him, is one such player at Florida State, he's started at safety, at linebacker and now they have him playing running back as well. A very interesting, super-athletic and highly versatile prospect that I've been following closely.
Below is a perfect example of what I'm talking about of Auburn's base nickel defense. $ represents the "star" safety in the alignment.
[ Edited by Phoenix49ers on Sep 23, 2013 at 11:21 PM ]