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Staturday: Defensive Metrics (Courtesy of grover)

When Blez first offered me this gig I knew that at some point defensive metrics would be brought up. A lot of time and energy has been devoted towards developing reliable numbers that can be used to evaluate pitchers and hitters but the defensive side of things lags well behind. I don’t know, maybe a lot of that has to do with fantasy baseball focusing all the scoring on pitching and hitting results. Seriously, has anyone ever heard of a fantasy league that awards points for defensive efficiency? I digress. Defensive metrics are just now starting to evolve to the point where they are both reasonably reliable and readily available to the general public which is why I wanted to be the one to talk about them.

If you really want to know how good a fielder is defensively you need to forget about the numbers and find a non-biased scouting report. At this time defensive ability is best measured or judged by the human eye, not by statistical systems.


I don’t trust defensive metrics to provide me with a consistently accurate measure of a player’s defensive ability as they’re too easily fooled. There’s a reason for that… they’re all flawed. So flawed, in fact, that there are several you should just flat out avoid. Anything you see on,, or should be ignored. Don’t even waste your time clicking on their links. I can’t tell you the number of times I looked up a player’s defensive performance on one metric, then cross referenced him with another system and have come up with conflicting answers. One standard praises the guy, the other says he sucks. The single best metric out there for public consumption is the Ultimate Zone Rating, created by Mitchel Lichtman. His UZR was so good the St. Louis Cardinals hired him to be their personal defensive metric maven; therefore you can no longer get a complete table of UZR numbers.

So where do we go from here?

Well, now that I’ve thoroughly undermined any confidence you may have had in defensive metrics prior to reading this article, let me start the building process. The reason defensive metrics are flawed is because they don’t contain enough data. First off, they ignore how a player positions himself prior to the ball being in play. The importance of pre-positioning should be obvious but I’ll go over briefly anyways. If a defender knows where the batter is probably going to hit the ball prior to the pitch even being thrown he can place himself in a position to easily field the ball. The easiest example would be to imagine a defense shifting to play a dead pull hitter. The 2nd baseman will slide over to his right until he’s practically behind the pitcher. The batter hits the ball up the middle, just to the 3rd base side of the pitching mound. The 2nd baseman takes a step to his right, fields the ball and makes a clean throw to 1st base. An easy out but most of the defensive metrics would award a bonus to the 2nd baseman for making a play so far out of his zone. His natural range had nothing to do with fielding the ball, his positioning was the primary factor.
The important thing to remember is that defensive metrics are not a magnifying glass that helps you clearly see what is there, they are a prism that distorts the image of what you’re trying to identify. The good news is utilizing one defensive metric allows all the subjects to be distorted in the same manner. Ah-hah! But which metric?

Accepting that there are flaws in all the accessible systems, the best place to look for defensive data is through The Hardball Times (THT) and their Revised Zone Rating System or RZR for short. Like just about every system, RZR looks at the percentage of balls that are hit into a defender’s zone and get turned into outs. THT has gone a step further then that and include Out Of Zone (OOZ) plays. An OOZ play is any out a defender makes while ranging outside of his zone. As I stated earlier, positioning can lead to a distortion of the out of zone data but OOZ is a solid statistical attempt to judge a player’s range on defense.

RZR and OOZ (weren’t those the names of the mutated bad guys in Teenage Mutant Ninja Turtles 2?) can be converted into Runs Saved, although I’m not entirely sure of the formula for this. Not to worry though, I’ve got the conversions on hand and I’ll share the numbers with you in a little bit. Hey, this is Staturday… I think I’m obligated to include some actual stats before I sign off! Still, I feel like the most important information I can pass on is this: In time the technology will be available to allow for a purely statistical way to evaluate defense but until then the best thing to do is mix existing analysis with observational reports (i.e. scouting reports) to best determine defensive skill.

(Well, I was going to go a bit more in depth on RZR but I can’t find the bloody link I need to continue, so to Hell with it! On to the numbers!)

Runs Saved (2007)

I’m focusing on the guys who project to be around in 2008. Remember, this is Runs Saved, a positive number is good and a negative number is bad.

1B: DJ = -4; Barton = -1
2B: Ellis = +15
SS: Crosby = +9; Murphy = -1
3B: Chavez = 0; Hannahan = +1
LF: Brown = +11; R. Sweeney = +1
CF: Denorfia = N/A
RF: Buck = +7; R.Sweeney = +1