Friday, January 14, 2011

The Giants Defense, Good or Bad?

Believe it or not the Giants were rated as one of the best defensive teams the last 2 seasons. This seems to go against what most people's eyes would have told them with some of the aging, slow, lumbering guys the Giants have trotted out in the field the last couple of seasons.

According to Fangraphs UZR measure the Giants finished 2nd in 2010 with 56.4 runs above average. In 2009 the Giants again finished 2nd with a UZR of 55.7. According to the fans scouting report in 2010 the Giants ranked 18th with a score of 1 run above average. In 2009 they were 26th with a rating of 26 runs below average.

So where does the divergence of what our eyes tell us and what is measured come from?

Again I turn to Fangraphs, Matthew Carruth has examined the difference between the UZR numbers and the fan scouting reports and noticed a few things that stood out:
The two biggest differences in FSR and UZR for the Giants come from Andres Torres and Edgar Renteria. Renteria is the biggest offender of the two. Fans rated Renteria well below average, a combined -21 runs for 2009 and 2010, but UZR saw the short stop as reasonably above average, a combined 2.7 runs. Andres Torres’ play is another example, garnering 29.4 UZR runs across the entire outfield but only 11 runs via FSR.

As big as the disagreement is on those two, the spread for the Giants does not come from a divergence of opinion on just those few players, but rather appears to be more of a systematic difference. Renteria and Torres totaled about 42 runs of difference between themselves, but the gap between FSR and UZR for the entire team is 137 runs.
 So what else could help explain the difference? To me there are a number of things.

First, maybe the fans are biased against some of the Giants older players simply because they are older or reputation. If they are discounting their play based on age and not something that they see that would introduce a bias. I think that this is plausible, Aubrey Huff, Pat Burrell, Freddy Sanchez, and Edgar Renteria don't exactly have great reputations but played solidly last season. You could also suggest that some of the younger players are not well known and could be underrated because they don't have a reputation. This could be the reason that Andres Torres was measured so low, he was spectacular but unknown to most people the last couple seasons.

Second, there could be something wrong with the UZR measurements. There could be some sort of systematic bias there that gives the Giants fielders a boost that is undeserved. There has been some studies looking into this but I don't know of any that looked specifically at AT&T park.

Third, the Giants pitchers induced balls in play that were more likely to fielded. I am not sure about this one as UZR should adjust for that as easy balls should be rated lower than things that are harder to field but I guess the simple act of more easy balls could inflate numbers. The other side is that fans tend to remember spectacular plays but forget the routine ones, if there are less opportunities to make a flashy play that could be a reason the fans rate the team lower.

I can't come up with any more explanations out side of random chance, sometimes you get outliers but that doesn't mean that either system is wrong but that is not a very exiting answer.

Anyone else have thoughts?

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