So much can change in 25 years. That statement is no truer than in sports, where 25 years is usually greater than the span of a player's entire career.

In that amount of time, players and coaches change, but, more importantly, so do styles of play. We see that across all sports today. Basketball is all about pace and space, baseball is all about pitching and power, and football is all about passing and dynamic wide receivers.

Different eras are shaped by new team strategies and organizational philosophies, so comparing players across several years can be quite difficult. At least, that has been the case until recently.

With the development of Pro Football Reference's approximate value (AV) metric, we can, in fact, compare player seasons from 2016 to seasons past (say, to 1992). This single number is representative of a player's season so that we may compare player and single-season values across NFL eras. If you want to know more about what all goes into it, you can find the details here.

As for the rankings, it's hard to break ties between players with the same AVs considering they play different defensive positions and accrue different stats in those capacities. So, players with the same AV are somewhat interchangeable as it pertains to their exact rankings.

No matter the order, here are the top 20 defensive player seasons of the last 25 NFL seasons.