March 15, 2017

In Part 7 of his fantasy baseball strategy series to make sabermetrics accessible to fantasy owners, Rick Lucks breaks down how to use FIP and xFIP to identify pitching sleepers and busts.

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 (4.19 in 2016).

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 fly balls 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.

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Editor's note: Be sure to check out all our strategy articles on how to win your fantasy baseball leagues: Our Sabermetrics series - Part 1: BABIP for Hitters, Part 2: HR/FB%, Part 3: Batted Ball Distribution, Part 4: Plate Discipline; Part 5, Pull %, Part 6: Lineup Slot and Counting Stats; Points League Primer; Using SIERA to Win Your League; How Your Brain Messes with Your Drafts; and Why You Shouldn't Overpay for Saves.

How to Use FIP and xFIP to Draft and Manage Your Team

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 the long season.

For example, some panicked when David Price got off to a bad start in 2016 with ERAs of 5.76 and 4.62 over the first two months. FIP and xFIP could have reassured them, as his FIPs (2.47 and 3.63) and xFIPs (2.56 and 3.84) in the same time frame suggested that Price was still pitching well. Price recovered somewhat for a 4.08 ERA in June before posting a 3.58 mark in the season's second half. Heading into 2017, he is still regarded as a good pitcher. The advanced metrics were right.

There are certain types of pitchers that may consistently defy FIP. The first is knuckleball guys, who have challenged DIPS theory since its introduction. Boston's Steven Wright had a 3.33 ERA last year, significantly better than his 3.77 FIP and 4.57 xFIP. This may lead us to conclude that his performance was a fluke, but he has consistently bested his FIP since his minor league days. Over Wright's MLB career, he has compiled a 3.58 ERA despite a 4.04 FIP and 4.57 xFIP. For Wright and other knuckleballers, there is no need to 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. Sonny Gray has been the poster boy for this group for a while. He posted a sterling 3.08 ERA in his first full season (2014) before following it up with an even better 2.73 mark the next year. FIP (3.46, 3.45) and xFIP (3.47, 3.69) did not care for him either season. He is obviously not a knuckleball guy, so sabermetricians predicted his decline every year, and they were always wrong--until they weren't.

In 2016, Gray's ERA ballooned to 5.69, a number bad enough to ruin a fantasy staff. His 4.67 FIP and 4.13 xFIP were better, but clearly indicate that he was not the same pitcher that he was before. Some are blaming health concerns for Gray's struggles, but I struggle to see the upside in doing so. Strikeouts are a key component of FIP, so pitchers who defy it are still lacking in a common fantasy category. Why risk another disastrous ERA for two category upside?

Personally, I'm leery of anyone's ability to consistently defy FIP, knuckleballers notwithstanding. Matt Cain's story is very similar to Gray's, and we know that it did not have a happy ending. 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. BABIP for pitchers will be discussed in Part 8.

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