This is an excellent discussion and delves into the actual process of the game and how teams win or lose games. I think the Buc's stat that Andy pointed out is telling, since they rank high in 3rd down efficiency and low in scoring D. So much of the game is so interactive that it is hard to isolate individual stats that can tell a true story.
Andy made another good point in that 3rd down efficiency doesn't tell a full story because can't register whether it was a 3rd and 2 or a 3rd and 22. Should you give the defense more credit for stopping the 3rd and 2, or do you give it more credit for creating the 3rd and 22 situation, and then stopping it. So much context is involved that doesn't show up in the stats.
So in the end, in a results oriented league, these kinds of stats, while interesting, and thought provoking, they AREN'T telling the full story. There is only one stat that does that, and that's scoring defense, and even that one bears some need of context, because it doesn't include garbage time scores or points allowed by the offense or special teams.
So maybe the key word here is CONTEXT. Understanding why the points were allowed and what needs to be done to prevent more. We also have to remember that defenses exist in an era were mediocre QB's complete 0ver 60% of their passes and good QB's complete 70%. It is a league where as recently as 2001 there were 11 QB's who had 19 or more picks in a season, last season there were none. The game is different. Trying to judge CB's who often playing different kinds of coverages, is virtually impossible. I mean how do you judge a CB who gets perfect position on a receiver and the pass is completed because he's 5'10 and the receiver is 6'4 and the pass was perfectly thrown. Did the CB fail? Was there anything he could have done that would have changed the results? Yet the game day weenies would call for his head because he was "beaten" on the play. The same goes for zone coverages, where great routes and perfect passes will always mean completions. The only reason zone D's are used is the fact that perfect passes and routes don't happen on every play.
Context is what you DON'T get from stats, and context is a critical element in judging a players' production. The coaching staff has that context because they know the calls and responsibilities, plus they understand the limitations and strengths of the players involve. Unfortunately, they don't share that information with us, or PFF or FO, etc. So what we get is their best ESTIMATIONS. In other words, they are interesting indications, but should never be used as fact, like they are so often by the fans and mediots.
