Is defense really that important in baseball?

[dickay]

Someone posted this in the Lowell thread;

Boston's Defense (UZR)
2009 : -16.3
2008 : 44.3
2007 : 24.1

1) Can someone please explain to me what UZR is, and how its determined.

2) Is one season really enough of a sample size to determine if a team or player is bad or good defensively? Bad luck, plays ruled errors that were hits, players who play with injuries....there seems to be alot of variables that come into any equation.

3) I hear of Bay being a poor defender. Since when did LF defense matter in Boston? Yes, if I had two guys near even in offensive performance i'll take the better "defender" but how much offense is needed to offset the poor defense?

4) Again regarding Bay or any defender who remains in their prime, are these statistics for defense solid enough to truly say as they do for Bay, he was a good defender early in his career and is now subpar? I again go back to sample sizes and variables.

Appreciate all unbiased input.

[Jeffy25]

Tang, this is all you

[HoustonGM]

1) Can someone please explain to me what UZR is, and how its determined.

In simplest terms, it's the number of runs above or below average contributed on defense.

Some reading on it:
http://www.fangraphs.com/blogs/index...-on-fangraphs/
http://www.baseballthinkfactory.org/..._2003-03-14_0/
http://www.baseballthinkfactory.org/..._2003-03-21_0/

(Note that it's been tweaked since those original articles were written by MGL, but that's the jist of it)

2) Is one season really enough of a sample size to determine if a team or player is bad or good defensively? Bad luck, plays ruled errors that were hits, players who play with injuries....there seems to be alot of variables that come into any equation.

To evaluate an individual player's actual defensive skill, one season of information is not enough. In general, one season of UZR is about as reliable as two months of offensive data. Three seasons of UZR is a good indicator of a player's actual defensive ability.

3) I hear of Bay being a poor defender. Since when did LF defense matter in Boston? Yes, if I had two guys near even in offensive performance i'll take the better "defender" but how much offense is needed to offset the poor defense?

A run saved on defense is equivalent to a run scored on offense.

4) Again regarding Bay or any defender who remains in their prime, are these statistics for defense solid enough to truly say as they do for Bay, he was a good defender early in his career and is now subpar? I again go back to sample sizes and variables.

When multiple defensive statistics (UZR, FRAA, RZR, TotalZone, etc.) show similar results AND it matches up with the narrative (in Jason Bay's case, the decline in defensive stats coincided with his knee injury issues), I think it's strong enough evidence to trust with reasonable accuracy.

[dickay]

I can have Derek Jeter and his offensive / defensive package or Ozzie Smith at the same age (32ish) with his offensive / defensive package. How are the so called experts comparing the two?

[dickay]

In simplest terms, it's the number of runs above or below average contributed on defense.

A run saved on defense is equivalent to a run scored on offense.

How do they "accurately" determine how many runs a guy gave up due to poor defense?

To evaluate an individual player's actual defensive skill, one season of information is not enough. In general, one season of UZR is about as reliable as two months of offensive data. Three seasons of UZR is a good indicator of a player's actual defensive ability.

So there is NO TRUE way to evaluate a TEAM defense since teams change dramatically over a three season period?

[HoustonGM]

I can have Derek Jeter and his offensive / defensive package or Ozzie Smith at the same age (32ish) with his offensive / defensive package. How are the so called experts comparing the two?

Let's see.

We'll use WAR...First, for Jeter. 2006-2009 were his age 32-35 seasons. TotalZone has him at -17 runs on defense over that period. Total WAR, including all offense and defense, of 20.1.

Now, Ozzie. 1987-1990 were his age 32-35 seasons. TotalZone has him at +74 runs on defense. Total WAR of 21.7.

A difference of 1.6 wins over the course of 4 seasons is really not that much, and should also be considered well within the margin of error since defensive stats are not as reliable as offensive stats, so, with reasonable accuracy, you can say that Ozzie Smith/Derek Jeter over the age 32-35 years were roughly equal in overall value.

[kenny1234]

How do they "accurately" determine how many runs a guy gave up due to poor defense?



So there is NO TRUE way to evaluate a TEAM defense since teams change dramatically over a three season period?

Team defense is essentially a meaningless concept. There are good fielding players, and bad fielding players. If you get enough bad fielding players on one team - then you have bad team fielding.

[KowboyKoop]

Is defense really that important in baseball?????

No need to discuss one single stat here.

Yes, of course it is important.

Now..discussing exactly how it is measured...discussing it's value as opposed to offense/pitching......those are very complex and the stats have a long way to go before FULLY being able to correctly answer those questions.....

but of course defense is very important.

[HoustonGM]

How do they "accurately" determine how many runs a guy gave up due to poor defense?

For UZR, I linked to the original articles on it. Each defensive stat does it somewhat different, of course.

So there is NO TRUE way to evaluate a TEAM defense since teams change dramatically over a three season period?

A teamwide UZR is a fine way to judge how well a team's overall defense performed in one year. The sample size for one individual player is not large enough over the course of one year. But, also, what kenny1234 said.

I prefer to look at a few defensive stats, though, and not just one. If a few systems all estimate a player at roughly the same level, I'm confident that they're accurate - ESPECIALLY if it matches up with the scouting view. My top three defensive stats would be UZR, TotalZone and +/-.

Generally, though, you'll see that the defensive stats actually do tend to match up with the "conventional wisdom" in most cases.

[SirKodiak]

Baseball

50% Offense, 50% Defense
Offense is composed of Batting and Baserunning
Defense is composed of Pitching and Fielding

Somewhere someone (I think it was Tango) came up with how much of Defense was Pitching, and how much was Fielding, but not sure where off the top of my head. I think it was 62% pitching and 38% fielding, on average, but don't quote me on that. Of course, a high K pitcher relies less on his fielders than a low K one does.

[dickay]

interesting HGM, reading that first link and i'm honestly not going to get too much into it but it practically starts off by saying that the UZR does not take into account OF arms!?!?!!? Isn't that a HUGE part of a corner outfielders defensive game, and doesn't that in itself take away alot of runs?

I'll maybe post more on it once i get through a bit more of it.

[SirKodiak]

interesting HGM, reading that first link and i'm honestly not going to get too much into it but it practically starts off by saying that the UZR does not take into account OF arms!?!?!!? Isn't that a HUGE part of a corner outfielders defensive game, and doesn't that in itself take away alot of runs?

I'll maybe post more on it once i get through a bit more of it.

It did not then, it does now, that was written a while ago and there have been many improvements.

[kenny1234]

Note also that the fielding statistics contain a ton of error. As an example, consider Jeter with TotalZone and UZR.

2003 - TZ = -14, UZR = -2
2004 - TZ = 4, UZR = 0
2005 - TZ = -3, UZR = -15

That is why you need to add up a bunch of years, and probably look across statistics that use different methods to decide that Jeter has been a below-average shortstop for most of his career.

That said, I think projecting defensive ability is far harder than offensive ability - lots can change over three years, and the statistics will not reliably pick up on improving, or more commonly, faltering defense.

[dickay]

RngR (range runs): The number of runs above or below average a fielder is, determined by how the fielder is able to get to balls hit in his vicinity.

This is the stuff that I don't get?? Seems like the margin of era much be HUGE. I've played the game, mostly a catcher but when I wasn't catching I was in the OF. How does one determine this? Balls move in flight, some are hit harder than others. If they say for example any ball thats hit within 15 feet of an OF should be caught...i'm mean really? Is that how they determine this?

[HoustonGM]

interesting HGM, reading that first link and i'm honestly not going to get too much into it but it practically starts off by saying that the UZR does not take into account OF arms!?!?!!? Isn't that a HUGE part of a corner outfielders defensive game, and doesn't that in itself take away alot of runs?

I'll maybe post more on it once i get through a bit more of it.

The first FanGraphs link was from when they first put UZR on the site. Since then, they've changed it. The UZR that is available now from FanGraphs takes into account range, arm, and errors.