http://www.behindthesteelcurtain.com/2009/3/10/77 ... nalysis-on
Here's is the main points, rankings based on raw defensive and offensive statistics for each team. The offensive statistics are being used here to determine how much work the defense needed to do to maintain these stats.
Adjusted based on the the teams they played, the Eagles are now number two:1 1977 Falcons
2 1976 Steelers
3 2000 Ravens
4 1991 Eagles
5 2008 Steelers
6 1973 Rams
7 1985 Bears
Conclusions.....1 1976 Steelers
2 1991 Eagles
3 1985 Bears
4 1977 Falcons
5 2008 Steelers
6 1973 Rams
7 2000 Ravens
I'll have to agree,Next in the raw numbers statistics comes the 1991 Eagles. They have many arguments to support them as the best of the remaining 3 defenses. They were the only defense (post '70s) to have a positive Opponent Offensive Factor. In fact, not only did they play a very balanced schedule in terms of top half and bottom half offenses, but they played 3 games against top 3 scoring offenses and 4 against top 5 offenses (both scoring and yards). Both of these are more than any other defense.
... the fact that the 1991 Eagles offense ranked 26th in yards and 21st in rushing yards, and the 1991 Eagles accomplishments become even more impressive. The only possible knock on them in this analysis is that the year 1991 had the 4th overall average offensive statistics.
....., I would actually give the '91 Eagles the nod, because they had a much less competent offense to complement them, particularly rushing the football, the safest and most tested way to keep your defense fresh, off the field, and limited in their exposure to the extremely capable offenses of professional football. Even though they gave up the most points per game in this analysis, their rush offense was terrible. Given the number of top 5 offenses that they faced, and their lack of a good rushing attack to keep those offenses off the field, the fact that they gave up the most points in this analysis doesn't bother me much.
In fact, after checking, I discovered that their offense had 43 giveaways that season. So, not only did the offense not help in terms of limiting offensive opponents' opportunities, it actually gave the opponent's more offensive opportunities. I was not able to find how many of them lead directly to points, but when you turn the ball over that often, it's amazing that they only allowed 244 points.