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Beyond the stats: Are Four Pass Rushers Enough?

Jim Schwartz is Buffalo’s new Defensive Coordinator and his hire comes with mixed feelings and reactions. Personally, I’m intrigued by the meticulous and numbers-based approach mentioned here and here. Beyond that, some conversation has developed regarding Schwartz’s philosophy of sending just four pass rushers, particularly the front four.

Conversation on developed between @JCStats,@MarkKelsoHelmet (give them a follow!), and myself about whether blitzing less is a good or bad thing. My initial reaction to the topic is twofold. First, Buffalo’s front four is as talented and imposing as any other in the league, and they should be able to generate pressure easily on their own. Second, Pettine’s scheme last season involved exotic blitzes involving defensive backs coming off the edge (and often dropping a lineman into coverage), which led to a much improved pass defense in 2013.

Using my pass defense data compiled throughout the season, I counted five or more pass rushers in 196 plays (about 32%). Those 196 blitzes occurred relatively evenly across the first three downs (61-68 per down), showing Pettine’s great ability to confuse opposing offenses and catch them off guard.

Buffalo blitzed three teams more than 40% of the time: the Buccaneers (50%), Falcons (41.5%), and Jets (40.3%). The three games that featured blitzes on forty or more percent of the pass plays were the three consecutive games from November 17th to December 8th. The Bills allowed an average of 165 net passing yards per game during that three game stretch, forty yards per game fewer than their season average.

161 of the 196 blitzes were of the five pass rusher variety. But the average yards gained per play didn’t vary much from the plays with four pass rushers. The Bills were able to generate more pressures under five man pass rushes than with just four rushers, but still allowed over four yards per play. When just four players went after the quarterback and forced a pressure, offenses averaged fewer than three yards per play. The table below compares four and five pass rush plays from Buffalo’s 2013 season.

Number of Pass Rushers

Basically the four man pass rush had a higher variance than the five man rush, but the overall averages are almost the same. The slight differences that do occur aren’t statistically significant, with the exception of the pressure rate. We can accept the alternate hypothesis and say the Bills get more quarterback pressures with five man pass rushes than with four. That’s pretty intuitive, but pressures don’t necessarily lead to successful plays for a defense.

Buffalo was able to pressure quarterbacks on 256 plays. The offenses still averaged 3.04 yards on those plays. 46 plays resulted in a gain of ten or more yards while the quarterbacks were sacked on another 56 plays. Offenses are still almost as likely to get a first down or a sack when their quarterback is under pressure.

Even the big plays allowed aren’t that much different on blitzing and non-blitzing plays. The Bills allowed big plays (gains of twenty or more yards) on 8% of all of the passing plays against them. Seven percent of the plays where they sent three or four pass rushers led to big plays, while ten percent of the plays with five or more pass rushers resulted in big gains. That difference isn’t significant though. A larger sample size is probably needed to do that significance test.

There’s a lot more to a pass defense than just whether four or five (or more) players chase the quarterback. Among the other variables are the caliber of players (from the defensive line to the coverage unit), the opposing offense, and randomness. So many things happen in any given play and so many things have ripple effects. Schwartz’s lack of blitzing in his defensive play calling doesn’t shouldn’t be concerning at this point.

The Bills have lots of talent up front (and in the secondary too) and we haven’t even touched the possibility of stunts, line shifts, or time to pressure. There’s always more than meets the eye in football.

Joe

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