Professional football has changed drastically over the decades, from players wearing leather helmets to today’s high tech helmets designed to prevent concussions and which require a safety certification before allowed to be used in games. Along with the changes in the game, the league and rules have changed, with the way the game itself is played slowly changing over time as a result of new rules, offensive and defensive innovations and the changing structure of teams and their rosters.
When rosters were expanded from 46 to 53 in the early 1990s, it led directly to the adoption of sub packages which allowed for greater rotation of defensive linemen, as well as the ability for coaches to have a lot more flexibility in terms of nickel and dime packages as well.