Sullymetrics: Dominance Factor
by Brett Sullivan
May 30, 2008
I wanted to create a statistic that shows to what extent a pitcher is dominating; something unbiased. Most importantly, I wanted it to be simple. I came up with this:
Dominance Factor (DF) = (Strikeout Percentage + Groundball Percentage – Walk Percentage) + ((Age-Level standard – actual age) *10)
Age-Level standard is an age that I assigned to each level in the minor leagues. The ages I chose are an approximate of what I believe to be average ages for an elite prospect in each league. Groundball percentages from Firstinning.com.
Low-A = 20.0
High-A = 21.0
AA = 22.5
AAA = 24.0
I used weighted averages to calculate Age-Level standards for players who have spent time at more than one level this season -- the same goes for K, BB, and GB%.
Here is an example Dominance Factor calculation:
Trevor Cahill DOB: 3/1/1988 (age: 20.2), 7.5 BB%, 31.1 K%, 63 GB%, 68.2 IP
31.1 K% + 63 GB% - 7.5 BB% = 88.6
(21 (A+) – 20.2 = .8) *10 = 8
86.6 + 8 = 94.6 DF
Cahill's score is outstanding. He leads all minor leaguers with 30.0+ innings pitched. Max Scherzer is the only player with a DF over 100 this season, as he truly dominated AAA in 23.0 innings this year.
The following is the Top 25 Dominance Factors in the minor leagues in 2008 to this point (Min 30.0 innings):