Sunday, February 06, 2011

Which Tigers Pitchers did the Best WERC in 2010?

Yesterday, I introduced yet another pitching statistic - Weighted Component ERA (WERC).  which serves as a supplement to the Defense Independent Pitching Statistics (DIPS). The WERC metric is similar to Bill James' component ERA except that it's based on linear weights rather than runs created.   If you read the previous post, you will learn how WERC is calculated and how it can be used. Today, I'll touch upon the main points and then use it to examine the Tigers starting staff.

Most readers of Tiger Tales are familiar with the Fielding Independent Pitching (FIP) statistic.  FIP estimates what a pitcher's ERA should have been based on events over which he has the most control - walks, hit batsmen, strikeouts and home runs.  Other DIPS (tERA, SIERA,etc.) do the same thing, but they add batted ball data (ground ball, fly ball, infield fly and line drive rates) to the equation.

All of the DIPS metrics remove results of batted balls (hits and outs recorded by fielders) and sequencing of events (e.g. stringing together hits and walks versus spreading them out throughout a game) from pitcher evaluation.  This is done because it has been shown that pitchers have less (although not zero) control over these things than they do on DIPS components

WERC estimates what a pitcher's ERA should have been based on walks, hit batsmen strikeouts and home runs plus results of batted balls (hits and outs).  So, it removes less potential noise than say FIP, but it still does not take sequencing of events into consideration.  It is useful for at least two reasons:
  • It can be used as an alternative to ERA for evaluating past pitcher performance.  It is especially useful if you think that a pitcher was either lucky or unlucky in his sequencing (e.g extremely high or low left on base percentage).
  • In cases where a pitcher's ERA is much different than his FIP, WERC can be useful in determining whether the difference was caused more by results of batted balls in play or something else such as sequencing.   
The table below compares Tigers starters in 2010 and 2011 on ERA, FIP and WERC.

Table 1: ERA, FIP and WERC for Tigers 2010, 2011 Starters

Some items which I found to be interesting are:
  • The Tigers five projected starters for 2011 - Justin Verlander, Max Scherzer, Rick Porcello, Phil Coke and Brad Penny - ranked ahead of the two departing starters - Armando Galarraga and Jeremy Bondermam - on both FIP and WERC.  That bodes well for 2011, but keep in mind the small sample sizes for Coke and Penny.
  • Verlander ranked only 11th in the American League on ERA, but finished third in FIP and sixth in WERC.  That is another positive sign because it's an indication that his ERA may be lower this year if he pitches similarly to 2010. 
  • Penny's WERC (4.10) was much higher than his ERA (3.23) and FIP (3.40) which says that he may have fared poorly on batted balls. His BABIP of .326 backs that up.
  • Porcello's ERA (4.92) was much higher than either his FIP (4.31) or WERC (4.42).  Because his FIP and WERC are so similar, the discrepancy between ERA and FIP would appear to be the result of sequencing rather than batted balls.  His 65.9 LOB% tells us a similar story.
I personally find WERC to be informative and will be using it again in the future, but I welcome any feedback from others.  If there is a better way to calculate it or if anyone has different thoughts on how it should be used, I'd like to hear them.

Note: Some of the data for this article were taken from Baseball -Reference and FanGraphs

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