Defensive Win Shares

Thinking about the impact of the Dodgers trading away Lo Duca, I noticed how much of his value is on defense, at least by the Win Shares method. As of Saturday, he had 3.4 fielding and 8.9 offensive Win Shares. I just don't think of him as being a brilliant catcher.

The Hardball Times has been updated since then but it looks like Lo Duca is especially strong on the defensive side. Montreal's Schneider is the only catcher in the National League who has contributed more on defense. In fact, the Win Shares system shows him to be the best defensive player with (or rather, formally with) the Dodgers. That's right, better than Beltre, Cora, Izturis or Bradley. Which doesn't seem right.

I don't really know the answer, but I wonder if this indicates that catchers get too much credit in the Win Shares system for team defense. Bill James created Win Shares in part to help evaluate the defensive contribution players make to their teams. He explains it all better than I can in sample pages from the book. Basically a teams wins are multiplied by 3 and divided between offense and defense based on the contribution of runs scored and runs allowed to the teams wins. Then defensive shares are divided between pitchers and position players, and finally between individual players.

I really like this top-down approach and I suspect that the system makes pretty good approximations. But it is hard to evaluate since there are so many little details. For instance, on a team with several ground-ball pitchers, you can expect more double plays. So the system discounts the value of double plays for shortstops and second basemen on those sorts of teams. It's logical and fair, but complicated. And all of that complication is hidden behind an innocent little number.

Evaluating a catcher's defensive contribution is especially complicated, since the common wisdom going back to the earliest days of baseball is that the catcher is the defensive leader of a team. As a consequence, catchers get more credit for team defense than other players. They even get some credit for team pitching, since they usually help the pitcher decide how to approach the batters they face.

Needless to say, the Dodgers have had exceptional defense over the last few seasons. So if catchers are given unfair credit for team defense, it wouldn't be surprising if Lo Duca is overrated defensively by the Win Shares method. On the other hand, if he's as good as the system suggests, we should see a dip in the Dodger's defense, Florida's defense improved and Lo Duca's August and September Fielding Win Shares approximate the first part of the season.

We'll see.