Dewan: How well do defensive statistics correlate?

From SABR member John Dewan at ACTA Sports on February 25, 2012:

We’ve put a lot of effort into improving defensive metrics in recent years, but how much progress have we really made? In the introduction to The Fielding Bible—Volume III, I said:

“For hitters, we might be at the 85-90 percent mark of being able to measure offense. We have a lot of good tools like OPS (on-base plus slugging), Runs Created, Wins Above Replacement. For pitchers, we are not quite as far along. Maybe we’re at the 75 percent level of understanding pitcher effectiveness with our numerical tools like ERA, Batting Average on Balls in Play, and Opponent OPS. For defense, ten years ago we were probably around the 10th percentile. Now with three volumes of The Fielding Bible under our belts, plus the work of many other excellent sabermetricians, we are probably in the 60-70 percent range.”

In our book, The Fielding Bible—Volume III, we put our newest defensive analytics to the test. If our statistics are measuring something meaningful, we would expect them to correlate well from year to year. In other words, since Evan Longoria topped all third basemen with 20 Defensive Runs Saved in 2010, we would expect him to remain one of the league’s top defenders at the position in subsequent seasons. (Longoria saved an estimated 22 runs in the field in 2011, also a league-leading total.)

To measure the consistency of our Defensive Runs Saved numbers, we calculated what we’ll call Even/Odd Year Correlations. We added each fielder’s Runs Saved totals from 2006, 2008, and 2010 and compared to the subtotal from 2007, 2009, and 2011, with the requirement that the fielder have amassed at least 667 innings in both subsets. We would expect the players with higher totals in even years to also have high totals in odd years, while players with low totals in even years should also tend to have low totals in odd years.

Read the full article here: http://www.actasports.com/statoftheweek

Related link: John Dewan will be speaking at the SABR Analytics Conference, March 15-17 in Mesa, Arizona. Learn more at SABR.org/analytics.



Originally published: February 27, 2012. Last Updated: February 27, 2012.

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