While searching through Advanced NFL Stats, I came across the defensive players stats. The first position I selected was Defensive Ends and I was very suprised at what came up. Near top of the list was our own Kyle Vanden Bosch. I clicked on a stat named “Tackle Factor” and he ranked 4th out of every DE in the 2010 regular season. I clicked on another stat, “Positive Win Probability Added”, he ranked 2nd. I could not believe it, so I began reading about these stats that I never heard about.
In this post I will talk about the stat named Tackle Factor. The regular tackle stat can be misleading, a team with a weak defense will give up longer drives resulting in more plays to get tackles. Also, more positions are prone to get more tackles. If you look at the top tacklers last year, the top 13 are linebackers. The idea behind the Tackle Factor (TF) stat came from the Range Factor stat in baseball. For many years, Fielding Percentage was used to measure the fielding of a player by basically measuring a player’s “non-error rate”. The stat is flawed because it can’t be an error if a player can’t get to the ball. Range Factor measures the percentage of assists and putouts a player has compared to the rest of the team.
TF measures a player’s percentage of tackles made compared to the team compared to the average percentage of tackles made compared to the team for that position. That is pretty bad definition so I hope this helps you understand.
What if we looked at the proportion of all 49ers tackles for which Patrick Willis was given credit? San Francisco logged a total of 832 tackles in the 2009 regular season, and Willis got credit for 114, a proportion of 13.7%. Willis is an ILB in a 3-4 scheme, and in 2009 the ILB position in all the NFL’s 3-4 schemes accounted for 21.5% of a team’s tackle total. Because there are two ILBs on the field at once, a single ILB could be expected to average half that, or 10.7% of a team’s total.
Willis’ 13.7% compares very well with his position’s expected tackle rate. His ratio of tackle percentage compared to the expected percentage for his position is 13.7/10.7, or 1.23. In other words, Patrick Willis has a ‘Tackle Factor’ of 1.23; he makes 23% more tackles than you’d expect from his position, which tells us a lot about his ability to shed blocks, get to a ball carrier, and make a tackle.
As mentioned earlier, KVB ranked fourth out of all DEs in TF last year. His TF was 1.14, that means he made 14% more tackles than the average defensive end. The best was Trent Cole of the Eagles who had a TF of 1.37 and Rams DE, Chris Long, had the worst on the list with 0.52. In 2009, the average 4-3 DE made 6.6% of the tackles on thier team. This stat shows how well KVB is at making a play and getting to the ball carrier.
This should give more reasons for opponents to fear the Silver Crush. If KVB is healthy for an enite year, the Detroit Lions will have the best defensive line in football without a doubt. In my next “How Important was Kyle Vanden Bosch in 2010″ I will discuss another advanced stat, Positive Win Probablity Added.