So I have sorta worked out a new metric meant to value impact plays. By impact plays, I mean sacks and TFLs. This is kind of the beta of this metric, because I'm not sure of how I've assigned values for sacks and TFLs and will likely end up tweaking it. Your input would be appreciated. I also thought about adding in interceptions, but that may not really fit into this framework.
Below is a list of the Top 10 "Impact" Players, accounting for TFLs and sacks. I assigned weighted point values for TFLs and sacks. I looked at a few different ways to do this, but ultimately came up with the following formula: 1 pt for every TFL, 3.09 pts for each sack. The rationale for this is based on the negative yardage these impact plays result in for the defense. I used 3.09 because it represents, by my calculation, the factor by which sack yardage exceeds TFL yardage. The basic idea is that, assuming the avg sack is 6 yards behind the line of scrimmage, a sack represents a loss of those 6 yards PLUS the opportunity cost of the pass that wasn't attempted. The average pass attempt in 2015 yielded 7.3 yards. So I added the 7.3 yards lost by not attempting the pass with the 6 yards lost from the sack itself. The only caveat here is I'm not sure if sack yardage is factored into total passing yardage.
I then looked at yardage lost for TFLs. These are almost exclusively rush attempts. The average rushing attempt in 2015 produced 4.3 yards. Therefore the sack that is negative 13.3 and the TFL is negative 4.3 yards, the sack is 3.09 more impactful.
I struggled with the TFL stat before settling on the above methodology. At first I thought I should count the avg amount of a TFL (estimated at -1). But then I concluded that because the avg yards per carry already includes negative yardage, this would be double counting. Again, your thoughts would be appreciate on this.
Anyway here are the Top 10:
1. Mario Williams, SEA -- 68.62 pts
2. Whitney Mercilus, SF -- 64.62
3. Robert Ayers, NYJ -- 58.44
4. Robert Quinn, ATL -- 56.08
5. Justin Houston, STL -- 55.35
6. Aldon Smith, TEN -- 53.44
7. Quinton Coples, WAS -- 50.26
8. Greg Romeus, SD -- 48.08
9. Da'Quan Bowers, BAL -- 45.99
10. Tank Carradine, DEN -- 44.9
I'll leave it at that for now. Let me know your thoughts on how to maybe improve this. Thanks!