Last month, my friend and colleague Derek Carty of The Hardball Times (THT) wrote a provocative article questioning the utility of FIP. Carty wrote, “While the original, underlying premise for FIP is sound, and while it’s absolutely better to use than simple ERA, and while there are certainly uses for FIP in some circumstances, for 99 percent of fantasy purposes, I ignore FIP completely and absolutely.”
Carty proceeded to list pitchers he believed were under and over valued by FIP, mainly due to their HR rate. He suggested that instead of FIP, we use LIPS (Luck Independent Pitching Stats). The problem with LIPS is that it takes a lot of work to calculate and is not freely available on a regular basis.
Since the main beef with FIP is HR rate, it should be relatively similar to use xFIP, a stat invented by THT which they describe as: “Expected Fielding Independent Pitching. This is an experimental stat that adjusts FIP and ‘normalizes’ the home run component. Research has shown that home runs allowed are pretty much a function of flyballs allowed and home park, so xFIP is based on the average number of home runs allowed per outfield fly. Theoretically, this should be a better predicter (sic) of a pitcher’s future ERA.”
As a general rule, most starting pitchers will have a HR/FB rate around 11 percent in a full season’s worth of pitching. However, there are always going to be exceptions to the rule. In 2008, Cliff Lee had the lowest HR/FB rate with a mark of 5.1 percent while Brandon Backe checked in with the highest at 16.1 percent. In 2007, the low was 4.1 percent while the high was 17.7 percent.
So, from a fantasy owner’s point of view, when evaluating pitchers should you look to normalize HR rate and use xFIP or are you just as likely to come out with a correct answer if you use FIP?
Here at the All-Star break, I have gone through and compiled a list of pitchers who have a difference 0.50 or greater between their FIP (taken from FanGraphs) and their xFIP. This list was done by hand, so it is possible I omitted someone by mistake. Please alert me if you come across someone I missed.
We have 34 people with a 0.50 or greater difference between their FIP and xFIP. Unfortunately, these are not all people you would want to have in a standard 12-team mixed league but the vast majority of these are roster worthy.
At the end of the year, I am going to come back to this list and see which one of these metrics was better for fantasy purposes. I am going to take the midpoint between their FIP and xFIP and compare it to their real life ERA in the second half of the season.
Using Greinke as an example, 2.55 is the midpoint between his FIP and xFIP. So, if Greinke’s ERA in the second half is 3.33, I will count that as a “win” for xFIP. On the flip side, if Greinke’s second half ERA is 2.22, I will count that as a “win” for FIP.
I am curious to find out what the raw score will be. My guess is that it will be fairly close to 50-50, with neither metric enjoying a huge advantage. Perhaps more importantly, I will also look to see if either metric does a better job of predicting a certain class of pitcher.
Regardless of what the results are in 2009, it is only one season’s worth of information.
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