Mientkiewicz and Defense

Here's an interesting story on ESPN that relates to the value of defense and particularly Doug Mientkiewicz and his acquisition by the Mets. Interestingly, the article notes...

Minaya figures first base is undervalued in the market place and in the minds of the average fan. "People take the position for granted," he said. He looks at a guy like J.T. Snow of the Giants, a smooth, graceful glove who "saves the Giants 10 games a year," and he anticipates something similar for his club with Mientkiewicz.

Once again, questions like these, while not being able to be answered definitely, can be estimated within a certain range. For example, it is well established that wins are purchased at the cost of 10 to 11 runs. Therefore, Snow would have to save 100 runs or more per season to actually save the Giants ten games. And as Baseball Musings points out, even if Minaya meant that Snow makes ten clutch plays per year that heavily impact the outcome of a game, it is still likely not true given his analysis of play by play data.

Although defense has historically been difficult to measure, a few systems have cropped up in recent years including Win Shares by Bill James, which calculates win shares for fielders, Ultimate Zone Rating (UZR) by Mitchell Lichtman, Defensive Regression Analysis (DRA) by Michael Humphreys, and David Pinto's Probabalistic Model of Range (PMR). What most of these systems have in common is that they estimate a difference on the order of 15 to 20 runs per season between stellar and average defenders at first base (the Win Shares difference is around 4 win shares which is 1.33 wins or 13 or so runs). PMR is the odd man out and sees a difference of about 40 outs which translates to around 30 runs although there is some debate on this topic. In either case Minaya is likely off by a factor of five or more.

To me, what this illustrates once again is that humans have difficulty accurately measuring a large number of observations, which leads to valuation based on general perception or a few memorable plays.