Defensive Metrics

[flyer85]

On ESPN Insider BP published a midseason fielding report.

http://insider.espn.go.com/mlb/insid...ory?id=4318647

The report utilized UZR and Dewans +/-. These seem to be regarded as some of the best metrics.

I was expecting that these would generally yield similar answers. I was in for a surprise. The numbers tended not to agree, especially in the OF.

Center field
Name UZR (Runs) Dewan (Plays)
Franklin Gutierrez 12.0 14.0
Matt Kemp 10.1 -1.0
B.J. Upton 5.4 -12.0
Mike Cameron 5.1 -3.0
Curtis Granderson 2.1 6.0

The most interesting results this season can be found in center, where players characterized as solid with the glove by UZR fail to make the leaders in the Plus-Minus system -- some even rate as below-average. In cases like this, it best serves interested parties to investigate the components that make up the systems. UZR breaks data down into the aforementioned categories of runs saved via the arm, double-play "turnability," error prevention and range. Plus-Minus also factors arm quality into the equation and breaks range up into different segments -- to left, straight on and to right for infielders, for instance. Carving your way through these data may help to explain the vast discrepancies. Unfortunately, there isn't much in the numbers capable of offering a definitive explanation.

I have always been skeptical of defensive metrics unless just using them to get a general feel (above,average,below). This seems to confirm my skepticism that there is any reliable way to try to assign some run value to defensive ability. I guess each person will have to determine how much they want to invest in any metric.

This stuff is still in its infancy but it seems to still have miles to go.

[jojo]

On ESPN Insider BP published a midseason fielding report.

http://insider.espn.go.com/mlb/insid...ory?id=4318647

The report utilized UZR and Dewans +/-. These seem to be regarded as some of the best metrics.

I was expecting that these would generally yield similar answers. I was in for a surprise. The numbers tended not to agree, especially in the OF.



I have always been skeptical of defensive metrics unless just using them to get a general feel (above,average,below). This seems to confirm my skepticism that there is any reliable way to try to assign some run value to defensive ability. I guess each person will have to determine how much they want to invest in any metric.

This stuff is still in its infancy but it seems to still have miles to go.

I don't pay for ESPN inside so I couldn't read the story. Was the list of CFers supposed to be the ones exemplifying discrepancies?

Really from that list only Kemp and Upton have UZRs and +/- scores that would radically disagree.

Also are the UZRs based upon BIS or Stats Inc data (using different data sources could contribute to discrepancies)?

[Scrap Irony]

Could it be a sample size issue with one of the metrics, and, if so, which one?

[Ron Madden]

I've always been skeptical of defensive metrics maybe someday someone will find a reliable way to assign run value to the defensive ability of any player at any position. IMHO we are not there just yet.

[flyer85]

I don't pay for ESPN inside so I couldn't read the story. Was the list of CFers supposed to be the ones exemplifying discrepancies?

they were listed in order of UZR

[flyer85]

Could it be a sample size issue with one of the metrics, and, if so, which one?

which is really the huge issue. Is one right and the other wrong? Are they both wrong? Hard to tell at this point.

[Jpup]

I have a terribly hard time believing the Reds have a good defense this year. I think Bruce has been great and Phillips as well, but the rest of them have been pretty average or below IMO. Dickerson has played well in center, but not so much in the corners.

[flyer85]

If there is a metric I do like it is DER. What percentage of balls in play does your team turn into outs. It makes sense although some of it has to be credited to pitching(or lack of it). It would make sense if your pitchers give up less line drives the DER will be higher.

[IslandRed]

I have a terribly hard time believing the Reds have a good defense this year. I think Bruce has been great and Phillips as well, but the rest of them have been pretty average or below IMO. Dickerson has played well in center, but not so much in the corners.

If there is a metric I do like it is DER. What percentage of balls in play does your team turn into outs. It makes sense although some of it has to be credited to pitching(or lack of it). It would make sense if your pitchers give up less line drives the DER will be higher.

Right now, the Reds are seventh in the majors in DER. Ninth after adjusting for ballpark factors. They're doing their job out in the field, at least.