Today's Philadelphia Eagles are far from the top of the NFL pantheon. They are coming off of a mediocre season, though they have hope to improve next year. But, looking back over the past three decades, at least one iteration of the team belongs in the conversation of all-time greatness. The people at Football Outsiders conducted a study to determine some of the top units in NFL history and found their pick at defense in 1991.

Football Outsiders makes the call

Football Outsiders used their defense-adjusted value over average (DVOA) metric to rate defenses over the past 30 years.

The metric zeroes in on yardage, turnovers, and points specifically. It also adjusts for the capabilities of the opposing offense in any given game. There's no one way to measure a team's overall effectiveness in any facet of the game, but DVOA had some high praise for the Eagles.

Football Outsiders put their 1991 DVOA at -42.4 percent, the best over the past three decades. They gave up 3.92 yards per play, which was one of the best marks in league history at the time. Yet they didn't even lead the league in points allowed for that season, finishing fifth in that statistic. Their biggest strength came in stopping the quarterback. They allowed just a 44.1% completion rate in the air, one of the best marks in league history.

The Eagles' team wasn't remembered for a dominant defense in 1991, though.

Struggles of the '91 Eagles

The 1991 Philadelphia Eagles, behind their dominant defense, seemed destined for great things. They had some stars on the offensive end and Reggie White to lead the way on defense. Then, within minutes of the start of the season, quarterback Randall Cunningham tore his ACL.

Just like that, all of the hopes and dreams for the team went out the door.

Despite the defensive domination, the Eagles failed to even make the playoffs. A season of defensive dominance was all for naught, as the team couldn't do what the 2000 Baltimore Ravens and 2002 Tampa Bay Buccaneers eventually did -- win behind a strong defense and a weak offense.

Instead, the history of a prime defense was left to languish in the wind. To this day, Philadelphia still has a grand total of zero Super Bowl titles (though they did win a few championships before the Super Bowl era). But, at least Football Outsiders recognizes the 1991 defense in a way that NFL audiences wouldn't have been able to when the calendar turned to January.