Thursday, May 26, 2005

Bill James on the Sacrifice Bunt

You might want to read this post first, as background.

In an interview with Baseball Digest Daily, Bill James has this to say about the sacrifice bunt:

[T]he general argument against the bunt seems unpersuasive to me. The essential argument against the bunt is that the number of expected runs scored after a bunt attempt goes down in almost all situations when a bunt is used, and the expectation of scoring one run goes up only in a few situations.

But this argument is unpersuasive, to me, because it assumes that there are two possible outcomes of a bunt: a “successful” bunt, which trades a base for and out, and an “unsuccessful” bunt, which involves an out with no gain. In reality, there are about a dozen fairly common outcomes of a bunt attempt. The most common of those is a foul ball, but others include a base hit, a fielder’s choice/all safe, a pop out, a pop out into a double play, an error on the third baseman, and a hit plus an error on the third baseman, or the second baseman if you’re talking about a drag bunt.

Some of those outcomes are reasonably common, and others are quite significant even if they are statistically uncommon. For example, if there is a 2% chance that the third baseman will field the bunt and throw it up the first base line, that has a huge impact on the calculations, even though it is only a 2% chance. It seems to me that the argument against the bunt is unpersuasive unless you account for the entire range of reasonably common outcomes.

... [W]e are in danger of replacing one dogma with another. And the analysis is not strong enough to justify that.

I can see now why some people find James frustrating. To me, his contrarian side outmuscled his logical side here. And it is hard to argue the point he makes, because he is absolutely right ... as far as he goes. But if you just go a little farther than James, you end up in a place full of absurdities.

Here's what I mean. James is perfectly correct to say that the general argument (like the one I laid out here) is incomplete -- an accurate probability analysis must consider all the possible outcomes of the bunt (foul ball, infield hit, error, throw to the wrong base, pop-up, etc.) But let's think about what he is saying: that adding all those other things into the mix might make the bunt a worthwhile strategy. Well, which of those events exactly? Certainly not the foul ball, pop up or double-play pop-up, those make you worse off. He must mean the hit, error, hit + error or throw to the wrong base, because those make you better off than trading an out for a base.

But none of those events are intended by the batter or his manager. They are trying to trade the out for the base. He's essentially saying, hold on, the bunt might be a good strategy because it could go wrong -- you might succeed in spite of yourself. That is hardly a defense of the sacrifice bunt.

But I do agree with James that we should not replace old dogmas with new ones. But the way to do that is to highlight the questions a manager should ask before he decides to bunt, and it is here where you can make profitable use of James' point. Those questions include:

(1) Can I afford to limit this inning to one run?
(2) Is the batter likely to strike out or pop-up?
(3) Is the batter likely to ground into a DP?
(4) Is the third baseman a bad fielder, likely to throw the ball away or make a dumb play?
(5) Is the batter fast? Might he beat out the throw?
(6) Is the batter able to get the bunt down?

If you are answering yes to these types of questions, you are making the case for the bunt. These types of questions are all derived from the "general argument" and James' points. Stats like those won't tell you what decision to make, but they can tell you the right questions to ask.


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