Defense

For every run scored, a run is allowed. That’s cemented in the rules of the game and the laws of physics. To score a run, someone else has to let a run score. While most of that allowance belongs to the pitcher, there are eight other players on the field with him at any given moment and they deserve some of the blame or credit for how often a run does or doesn’t score.

Unfortunately, for most of baseball history, we’ve had exceptionally lousy practices for measuring defense. Errors and fielding percentage seem to make sense at first but if you peel back the onion at all, they just don’t get the job done. Defense is a meaningful slice of run prevention and we care about measuring run prevention, ergo, we need to do a decent job of measuring defense. How do we go about doing that?

This section of the Library walks you through that process, chronicling some of the different tools we have at our disposal. There are going to be some changes happening in the next few months and refines along the way, so think of this as a bit of a living organism.

Some additional, incomplete links (suggest others!):

Sabermetrics 101: Defense – Lookout Landing

Framing the Framing Debate – Lookout Landing

What Mean Do You Regress To? – FanGraphs

Defense and Inferential Statistics – FanGraphs

Evaluating Defense – Beyond the Boxscore

UZR: 2008 to 2009 – FanGraphs

Defensive Metrics, Their Flaws, and the Language of Writers – FanGraphs

The Beginner’s Guide to Measuring Defense – FanGraphs





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

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BillYoImACubanBBrianjonesy369Ernie Vanholland Recent comment authors
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Sam
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Sam

Where does the “Scp” (scoops, presumably) data on the player pages come from, and how is it defined? Thanks!

Ernie Vanholland
Guest

This web site doesn’t render correctly on my apple iphone – you might wanna try and repair that

jonesy369
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jonesy369

In the Team Statistics display, what exactly is “Fld”? Obviously some kind of measure of defense, but what measure? UZR? +/-? FRAA? It doesn’t seem to be in your glossary.

Brian
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Brian

@jonesey Fld is simply the player’s UZR at each position played during the season summed.

YoImACubanB
Member
YoImACubanB

could you please change some settings so that you are able to hover out the categories and a little bubble window pops up with what the abbreviation stands for. It would be a little easier to do research if we knew what we were looking at =)

Bill
Guest
Bill

This is very true — a lot of these abbreviations you guys use are not listed in your glossary, and these days it is so easy to have that info appear as hover text, in fact it’s pretty standard on stats websites now. If you want to spread the gospel of sabremetrics, maybe it’s better if it’s not all in Latin. It’s a bit much to expect us new visitors to go google every heading. At least they should be in the glossary, and it looks like many of the headings are not. This is a major UI deficiency on… Read more »