On ESPN Insider BP published a midseason fielding report.
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.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.
This stuff is still in its infancy but it seems to still have miles to go.