Been thinking about this for a while and thought it would be a good topic.
In the old NFL you had 22 starters, 2 specialists, and a bench. The offensive allignment and defensive allignment never varied much personnel wise and you just strapped em on and played.
Over the last decade or more there has been a dramatic change in that formula, but we still identify 11 'starters' on offense and 11 starters on defense as if it was still 1970.
The reality is most teams spend as much time in specialty allignments as they do in their base allignments - Pats played base defense under 50% of the snaps last year for example.
So looking at defense - an average team has 4 DBs and maybe 2 LBs that average around 80+% of the snaps. And they probably have 2 DLine that average 70+%. So that is 8 traditional 'starters'. The other 3 or 4 defensive 'starters' are really rotational players selected out of a pool of players that all play at least 30% of the snaps - so you have 2 additional DBs for nickel and dime formations, 2 or 3 situational LBs, and 3 or 4 situation DLine. These guys provide serious production to the overall defensive stats. (e.g. 2 years ago I think Anderson had 6 sacks in situational duty prior to when Carter went down and his playing time went way up.) And these guys are not the traditional definition of 'bench' or back-ups. And we should really be thinking of them in the same light as the 'starters' in terms of the team make-up. I would say the 'starting defense' is really composed of around 16 players, and not 11.
Looking at Offense - specific to the Pats. Again traditionally you have 11 'starters'. But the reality is you have 5 OLine and a QB that play 90% of the snaps, 1 tight end and 2 receivers that play 80+%, and then it is again a rotation - situational allignments. A platoon of 3 backs, none of whom top 50% of snaps, another 2 TE and 1 or 2 receivers that see 30+% of the snaps. So 9 traditional starters and 6 or 7 rotational players. Again somewhere around 16 players that represent the totality of the 'starting offense'. The numbers may vary a little by team and offensive scheme but the variety of formations used by most teams is similar to the Pats.
I just thought this was interesting when we get into discussions of drafting and 'building depth' vs. getting 'starters'. And when looking at the versitility that BB values so much.
The Pats are really looking to build a roster of 32 'starting' caliber players and a bench of 20+ injury back-ups. That requires a different mindset than looking to have 22 'starters' and a bench of 30+ players. And it also has serious salary cap implications. And it has bearing on the type of players that comprise the bench - players that can provide spot duty in multiple roles is very important when you only have 20 instead of 32 back-ups.