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Jeff's Special Sauce - Easy Formula for Evaluating Pitchers

I am always looking at ways to make complex formulas simpler. For pitchers, I started using just K/9 minus BB/9 to measure how good they were. It has not been a bad to evaluate pitchers from one season to the next, but I haven't been able to take into account any batted balls. I really wanted to include ground ball rate since it prevents home runs and correlates decent from year to year as seen from this information from "Baseball: Between the Numbers":


Winning percentage - .204
Batting average on balls in play (BABIP) - .272
ERA - .380
Home runs per batter faced - .470
Hits allowed per batter faced - .499
Walks (W) per batter faced - .676
Strikeouts (SO) per batter faced - .790
Ground ball (GB) percentage - .807


Using the numbers that are somewhat easy to find and correlate easy from season to season, I came up with the following formula:


Jeff's secret pitching sauce = K/9 – BB/9 + [(Ground ball Percentage in Decimal format)*10]


The values doesn't represent any existing number, but correlates decent with FIPs (r-squared = -0.67) and xFIPs (r-squared = 0.91) when looking at all the qualified starters over the past 5 years.

Here is a list of how often values showed up for the starters I looked at:


Sauce Percent of Qualified Starters
12 0.7%
11 6.2%
10 10.2%
9 15.6%
8 18.5%
7 22.5%
6 18.2%
5 6.4%
4 1.7%



An equation that could be used to compare it to ERA is the following:

ERAs = -0.31*(sauce) + 6.78

I used the equation recently to look at some minor league pitchers over at

I never expect it to catch on, but it is an easy number to figure in your head given the 3 values.  Also, It should be relatively constant from season to season. Let me know what you think.