Monday, 3 October 2011

Informing The Masses: Part 1. Fielding Independent Pitching

The first thing I want to do is start off by saying, that this is not meant to insult anyone's intelligence or how informed they are. This is just meant to simply explain these advanced statistics, in a way that makes a rational argument.

Alright. Lets look at the current generic standard of evaluating how a pitcher has performed, ERA.  Looking at ERA, it is a good natured stat, that attempts to remove defense from the pitchers stats but it really doesn't do the job. Errors only account for balls that players get to so a poor fielding shortstop like Derek Jeter, will not be accounted for in ERA because of his lack of range, but someone like Yunel Escobar who gets to alot more balls, therefor makes more errors. 

There are many versions of FIP.  xFIP is a predictive stat, telling what a player will likely do in the future. bbFIP, which is my favourite for evaluating pitchers, breaks it down into what type of contact a pitcher induces.  But I'll explain these versions later.

The FIP Calculation
First off, there are values assigned to Homeruns, Walks and Strikeouts.  How TangoTiger, the creator of Fielding Independent Pitching metrics, arrived at these values was linear regression to find the average value that each true outcome (HR, BB, K).  What he came up with is this.

HR = 13
BB = 3
K = 2

This leads to the formula FIP =  (((HR x 13) + ((BB + HBP - IBB) x 3) - (K x 2)/IP) + Constant to convert to ERA.

This regulates things pitchers have little to no control over, BABIP or Batting Average On Balls In Play.  
The problem with FIP is, it can over value pitchers who give up hard contact without the ball leaving the park, striking out lots and walking few. One such example is Brandon Morrow, as Jays fans know, he strikes out a tonne, walks few compared to how many he strikes out, but gives up lots of hard contact.Another problem is that it doesn't account for home ball park, so pitchers in pitchers parks tend to have a slightly inflated FIP. It also doesn't account for how pitchers do with runners on base.

The top 10 in FIP for 2011 were:

As you can see from the chart, NL Pitchers are definitely favoured by FIP, and that is due to the fact that they face the pitcher once every 9 batters, and the usual likely K. Matt Cain, Madison Bumgarner, Clayton Kershaw, and Dan Haren play in pitcher parks. That is not to say that these pitchers are products of their park. They all combine great K/BB rates and don't allow hard contact.

For tomorrow's installment, I'll breakdown xFIP and bbFIP..


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