Using Sabermetrics for Fantasy Baseball Part 6: FIP and xFIP

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The first advanced pitching stat most fantasy owners encounter is FIP. FIP stands for Fielding Independent Pitching, and attempts to measure a pitcher's actual skill instead of the effects of luck or his supporting cast. According to the DIPS theory that the metric is based upon, pitchers control only Ks, BBs (and HBP) and home runs allowed. Therefore, Ks, walks and dingers are the only inputs to determine the number.

Calculating FIP requires way more math than most fantasy owners are comfortable with, so don't worry about the formula. For fantasy purposes, it is sufficient to understand the three primary inputs listed above and the fact that the stat is on the ERA scale. That means that if a FIP would be a good ERA, it is a strong FIP. The math is perfect, meaning that the league average FIP and ERA are identical (3.96 in 2015).

Sometimes xFIP is cited instead of FIP. The x stands for expected, and the stat is rooted in the fact that HR/FB varies for pitchers just as much as hitters. While FIP uses a player's actual homers allowed, xFIP charges him with a league average amount of homers based on his flyballs allowed. Some pitchers are consistently more or less homer prone than average, but studies show xFIP is a more reliable predictor of future ERA than regular FIP.

This predictive nature of FIP and xFIP is the reason fantasy owners should care about them. Both metrics predict future ERA more reliably than ERA itself, making them a good go-to stat to determine if an early breakout may be for real or if a struggling superstar is likely to rebound. All things being equal, it is generally expected that a pitcher's ERA will regress towards his current FIP and xFIP over a long season.

For example, some panicked when Clayton Kershaw got off to a bad start (for him) in 2015 with ERAs of 3.73 and 3.97 over the first two months. FIP and xFIP could have reassured them, as his FIPs (2.82 and 2.43) and xFIPs (2.00 and 2.36) in the same time frame suggested that Kershaw was pitching as well as he usually does. The advanced metrics proved to be correct, as no one remembered his subpar start when he struck out his 300th man in September and contended for the Cy Young award.

There are certain types of pitchers that may consistently defy FIP. The first is knuckleball guys, who have challenged DIPS theory since its introduction. Toronto's RA Dickey had a 3.91 ERA last year, significantly better than his 4.48 FIP and 4.72 xFIP. This may lead us to conclude that his performance was a fluke, but he also turned the trick in 2014 with a 3.71 ERA against a FIP of 4.32 and an xFIP of 4.14. Over his career, he has a 3.97 ERA against a 4.32 FIP and 4.21 xFIP. For Dickey and other knuckleballers, don't bother with FIP.

The other type is simply called a "FIP-beater" that manages to control the quality of contact against him to the point that he outperforms his peripheral stats. For a long time, Matt Cain was the poster boy for this group. From 2009-2012, Cain posted very strong ERAs without the FIP or xFIP to back them up. He was obviously not a knuckleball guy. Sabermetricians predicted his decline every year, and they were always wrong--until they weren't.

In 2013, Cain's ERA ballooned to 4.00, a number slightly worse than his 3.93 FIP and 3.88 xFIP suggested he deserved. His 4.18 ERA the next year was worse than his 4.01 xFIP but better than his FIP of 4.58. Last year, his 5.79 ERA, 5.54 FIP and 4.94 xFIP all suggested a bad season. If Cain discovered some secret to beating FIP, he seems to have lost it.

Now, the poster boys for FIP-beating are relievers like Tyler Clippard, whose low innings totals and lack of saves or Ks make them undesirable fantasy assets even if they can beat FIP. Personally, I'm leery of anyone's ability to consistently defy FIP, knuckleballers notwithstanding. There is an ongoing debate in the sabermetric community though, so my word is not gospel on the subject.

To conclude, FIP and xFIP are metrics that try to determine the ERA a given pitcher deserves based only on the outcomes he actually controls: Ks, BBs and home runs allowed. While FIP uses the pitcher's actual homers allowed, xFIP regresses it to the league average figure. Both metrics are on the ERA scale, and may be used to predict future ERA with more accuracy than ERA alone. Of course, we can also predict how some of the "luck" that separates ERA from FIP will play out, gaining an additional edge in fantasy leagues. BABIP for pitchers will be discussed in Part 7.

 

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