FanGraphs Glossary: The Winter Cleaning

As pointed out on Twitter today, there’s some good news for baseball fans today: the wait until Spring Training is officially half over. The middle of February is looking closer and closer now that January is a few days away, so before we know it, pitchers and catchers will begin their yearly migration down to the warmer climes. Our long, dark teatime of the soul is all but over.

But this is bittersweet news. Yes, the wait until Spring Training is almost over, but the coming month and a half is typically the slowest, most painful time of the offseason. The Winter Meetings have passed and baseball news has slowed down to a crawl, so there isn’t much to keep us baseball-philes content. This January promises to be more eventful than most, considering Prince Fielder is still on the market and there are multiple potential trades that may happen, but I’m not about to set my expectations too high.

Since things can get so slow this month, this is typically the time of the year when I update and re-edit the Sabermetric Library — a mid-winter cleaning, if you will. I haven’t begun dusting out the cobwebs yet, though, as I’d love to get input on what people would like to see this time around. And so…

  • Are these any pages in the Library you think badly need an edit? Is there anything you’d like to see added to any particular page?
  • Are there any new pages or articles you’d like to see added to the Library?
  • Any new links that I should be sure to include in the Library?

In short, if you have any ideas on how to improve the glossary here at FanGraphs and to make it more useful, please share! I’ll be spending the next month or so making edits and changes, and I welcome any ideas.

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Steve is the editor-in-chief of DRaysBay and the keeper of the FanGraphs Library. You can follow him on Twitter at @steveslow.

28 Responses to “FanGraphs Glossary: The Winter Cleaning”

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  1. MauerPower says:

    More of a question than anything. In the SIERA page it says SIERA isn’t the end all be all type stat and talks about how FIP and xFIP still have their uses. It also says how you should be balanced when using them. What type of advantages does FIP/xFIP have over SIERA?

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  2. Jacob Smith says:

    Less reliance on inherently flawed batted ball data, more focus on absolute events.

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    • Barkey Walker says:

      What, exactly, is the difference between the call on a pitch the batter takes and these references? They happen only because an official say they happen, and in that way, they are the same.

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    • jim says:

      yeah, things that are totally under one party’s control, like say, strikeouts, walks, and home runs…. if only there were some sort of metric encompassing that….

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  3. Barkey Walker says:

    I would suggest a FAQ that addressed common criticisms of saber stats and probably also included acknowledged criticisms of them too.

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  4. Anon says:

    From wRC+: wRC+ is also park and league adjusted, meaning you can use it to compare players that played in different years, parks, and leagues.
    An extensive explanation of the park and league adjustments would be nice.

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  5. bender says:

    No one uses wRC+ correctly (not even FanGraphs writers). The number of points from 100 is double the percentage difference, i.e. a wRC+ of 110 doesn’t mean 10% above league average, but rather 5% above league average. That’s how people can have negative wRC+s. I really wish someone could get it right.

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  6. RMR says:

    Tool tips — or at least a search link on player pages. While the glossary/library is nice to have, it’s quite a pain to try to dig through it to figure out what some abbreviation means or how it is sourced/calculated.

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  7. Snaztastic says:

    Not exactly in the scope of the glossary, but I’ve wanted to see “league average hitter”, “league average starting pitcher”, and ‘league average relief pitcher” pages for quite some time. It would allow for quick reference to the league average definitions, as well as the general trends over the years.

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  8. Cap says:

    *As previously mentioned, links from player pages … it would be great if you could click on things like wOBA, wRC, Pitch Values, etc and be brought to an article that explains the stat in detail.
    *Add a “Show Averages” button to more/all sections of player pages. I find these very useful.
    *A button that tells you what all the PitchF/X pitch type abbreviations mean. I have no idea what some of these mean … what pitch does “EP” stand for?
    -And keep up the good work. I love the site!

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  9. Sam Menzin says:


    I’ve mentioned these to you before, but adding MLB service time figures would be very helpful, as well as some arbitration class tracker (denoting supertwo, or 2nd time arb eligible for instance).

    Also, baseball-reference has league averages much more readily available if you click on “more stats” (for OBP, SLG, etc.)

    This has been commented on before, having the sort tool when you click on a statistic go to the highest value, instead of the league worst (lowest, since ERA would be the best).

    Maybe include some type of scroll over glossary on player pages (ala BR). For instance, some new readers might not know what O-Contact % means, and I believe it’s harder to find that out now then it used to be.

    I know Joe Lefkowitz’s site does this, but having Contact % and BABIP figures for individual pitch types and batted balls would be awesome!

    You do the best job on the best site–looking forward to new adjustments.
    Thank you!


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  10. Brent says:

    When I run across an acronym that I’m not familiar with, it can be hard to find the definition. The menus used to organize the glossary are not always intuitive – I think it might be more straightforward to have a simple alphabetic index.

    I don’t think that glossary entries are available for all of the statistics shown in the various tables – or maybe I just have been unable to find them due to the navigational difficulties mentioned above. Please make sure that glossary entries are available for all statistics.

    It would also be helpful if you made sure that each definition includes some basic information – for example: Is the statistic park adjusted? What units is it measured in? (e.g., runs, wins, index relative to league average) If it’s measured “relative” to some parameters (e.g., run and win values for statistics like RE24, WPA), how often are the parameters updated and what timespan is used to calculate them? If the original author of the statistic is known, it may be useful to cite the author – giving them a bit of credit and giving the reader a source to go to for more information.

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    • Mike says:

      Maybe the ‘basic (stat) information’ you mention could be in a standardize format across all relevant stats that says if it’s position adjusted, park adjusted, etc.

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  11. How far are we away from having batted ball speeds? It would be great to get some see one guy with a 20% line drive percentage with a significantly higher batted ball speed over another with the same line drive percentage (as well as other hit trajectory types, of course).

    I also agree with the comments that hovering over a stat type would give a brief definition when they can also be sorted.

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  12. Oscar says:

    Could xBABIP be added to all player pages? Please.

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  13. Stros in 2020 says:

    I also frequently try to use the glossary and have yet to be able to open it.

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  14. David says:


    As a relative newcomer, it would be really helpful to link to the glossary entry from the stats pages or have a bubble pop up with a short definition or something, it’s difficult to find the definitions for each different thing and then if you forget you have to go back and search through the glossary to find it. If it were right there when you’re looking at the stats it’d be a big help!


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    • MH says:

      It did used to be like that, where a bubble would pop up when you moused over a stat title on the player pages, but for some reason when they changed table formats recently they took that feature away. The reasoning may have been explained somewhere, but if it was I missed it, and I agree that it was very useful and I’ve found myself missing it on a number of occasions.

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  15. MH says:

    Svlad Cjelli reference!! Anyone catch the Dirk Gently TV pilot they aired on BBC4? It wasn’t amazing or anything, but it was probably the best Douglas Adams piece put to film, at least since the original Hitchhiker’s miniseries (which, honestly, I wasn’t in love with, but it was obviously better than the American movie that, although well cast, was otherwise a disaster) or maybe some of his original Dr. Who episodes (which I’ve never gotten around to tracking down and watching). Anyway, it looks like the Gently pilot did get picked up for a miniseries, only three more episodes for now, but it was pretty decent. Just a heads up for any other Adamsophiles out there.

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  16. TK says:

    I know it’ll never happen, but brWAR would be nice.

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  17. MauerPower says:

    What about a stat called wOBA-?

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  18. lester bangs says:

    As Cap said:

    *A button that tells you what all the PitchF/X pitch type abbreviations mean. I have no idea what some of these mean …


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