When judging total defense in the NFL, many often point to yards allowed as the primary measure for a unit's effectiveness. ESPN analyst Tedy Bruschi sees that as a flawed analysis.
Bruschi has put together his own formula on how best to measure defense, and it goes back to five core principles he was taught as a player:
Don't let them score (points per game; only on offensive plays from scrimmage)
Take the ball away (the importance of turnovers)
Get off the field (third-down conversion rate)
Situational defense (red-area efficiency)
Disrupting the franchise QB (sacks)
By rating each NFL team in these categories, it produces a league-wide defensive index that purposely overlooks yards allowed as a measure to gauge the effectiveness of a defense. Why no yards? With more spread offenses and prolific passing attacks in today's NFL, Bruschi views yardage rankings as overrated because many teams have the ability to go from 20-yard line to 20-yard line on a regular basis.
Thus, Bruschi's "defensive index" places a heavier emphasis on the growing importance of "situational" football.