There have been plenty of people who have pointed the points allowed to try to say this was the 2nd best defense in the NFL. There were other posters in another thread using this stat to say that this defense is better than defenses such as Denver and Minnesota. That ignores plenty of context - the quality of opposing offenses played, how long they are on the field over if their offense can't move the ball, etc. This defense is not horrible. Those that say it is forget the 2011 defense. This defense is more talented and doesn't have a WR playing CB and a goon squad at safety.
That said, I don't think this defense is top two in the NFL. They tighten up in the red zone but have trouble getting off the field on 3rd down which then takes away snaps for our offense. I've been of the opinion this entire season that this defense is somewhere in between the one that shut out Houston and the one that got ***** made by Seattle. Have they really improved? Hard to say when your competition is the 49ers, Jets, and Rams. I suppose MNF is as good a marker as any we'll have the rest of the year. I hope so. I'd love to see a more stout defense going into the playoffs. In the end, relying too heavily on PPG to measure the defensive side of the ball is reaching at best, folly at worst. The Cowboys currently rank 5th in PPG. Do you really think they're a top five defense or do you think they benefit from other factors? Would you take them over, say, the Broncos (6th) and the Lions (11th)? Context is key. Neither side, the side that says the defense completely sucks and the side that tries to make them out to be a top two unit, is correct. The answer is somewhere in between.
Points allowed are far and away what is most important. All of those other factors are more like compensating factors.
But first, we need to be clear. You can only realistically judge how a defense has played, not how good it is. Trying to guess at how it would play in some unknown future game is ridiculous, and if it were possible we would all be professional football gamblers.
So, judging how a defense has played points allowed is far and away what matters most. Almost every other statistic can only be used as an argument for why a defense should be better or worse (ie allow more or less points). The argument about taking opportunities away from the offense theoretically may have merit, but in reality, it does not. There is miniscule difference in low point defenses and how much time they spend on the field, and even where there could be a factor, getting off the field sooner by allowing points isn't helping anyone. For example, as the argument applies to the Patriots, they are 7th in defensive time of possession. Compared to #1, they have faced 16 more defensive snaps, or 1.25 per game. That is not keeping the offense off the field. Sure if your defense is on the field for 8 minute drives every time it keeps your offense off the field, but in the real world that just doesn't happen and this is a misunderstood non-factor.
There are certainly other factors in HOW you ended up with a points allowed number. If your offense allowed points, that shouldn't count against the defense, if they turn it over often, or in bad field position that is a factor also. No statistic is football has any value all by itself without context.
However, focusing on other statistics as more relevant than points allowed is wrong. Whatever you need to do with yards, sacks, completions, conversions, red zone, run D, etc, etc to keep points off the board is irrelevant if you keep them off.
Strength of opponent is also a shaky argument. You can only play who you play, and it is absolutely not a fact that each team does better against each weak team and worse against each good team. Matchups matter. But in the end trying to factor something like that in is trying to guess at what will happen in an unplayed game, and it now just becomes conjecture.
Points allowed, adjusting for the situation under which they were allowed (turnovers, garbage time, defensive and st scores, etc) are the way to judge what a defense has done, with takeaways as a heavily weighted secondary factor.
Really, points allowed is the starting point, adjustment should be made for situation and circumstance and then takeaways should be a heavily weighted second factor to further adjust. Yards, eye test and stylistic factors aren't really relevant.
