A prevailing philosophy in the fantasy football world is that defenses “don’t matter.” This idea, like its father, “RBs don’t matter,” needs further explanation, because, come on.
In reality, the reasoning behind ignoring opposing defenses comes down to the fact that we often overrate weekly matchups when making roster decisions. It's useful to consider matchups when digging into the waiver wires and attempting to find a big week from a boom-or-bust player. But the idea that you should ever fade top-scoring skill players due to a bad matchup is generally false.
The matter is further complicated by the reality that we sometimes confuse which defensive statistics impact which positions. Or we overlook roster turnover and schematic changes. Sixteen-game samples are incredibly small indicators for anything, and football’s inherent randomness continues to make the sport more difficult to predict than just about any other.
This doesn’t mean we shouldn’t try to improve our understanding of the impact defenses have on offenses. More and more data has become available to better judge defensive talent over the years, and we have seen the truly elite positional groups on the other side of the ball yield consistent domination for extended stretches.
What follows is a breakdown meant to improve our ability to incorporate defensive performance into fantasy football decision-making. (For a breakdown of which offenses have the cushiest start to the season by positional strength of schedule, click here.)
A dominant defensive line is obviously not ideal for an offense to come across, although sometimes it’s actually a net positive for the passing game because the secondary is weak enough to consistently encourage opposing QBs to throw the ball all over the field. On the other hand, a stingy secondary paired with a weak front-seven can result in offenses running the ball to their heart's desire.