There’s been some discussion lately on Twitter about the sacrifice bunt. Of course it is used very little anymore in MLB other than with pitchers at the plate. I’ll spare you the numbers. If you want to verify that, you can look it up on the interweb. The reason it’s not used anymore is not because it was or is a bad strategy. It’s simply because there is no point in sac bunting in most cases. I’ve written about why before on this blog and on other sabermetric sites. It has to do with game theory. I’ll briefly explain it again along with some other things. This is mostly a copy and paste from my recent tweets on the subject.
First, the notion that you can analyze the efficacy (or anything really) about a sac bunt attempt by looking at what happens (say, the RE or WE) after an out and a runner advance is ridiculous. For some reason sabermetricians did that reflexively for a long time ever since Palmer and Thorn wrote The Hidden Game and concluded (wrongly) that the sac bunt was a terrible strategy in most cases. What they meant was that advancing the runner in exchange for an out is a terrible strategy in most cases, which it is. But again, EVERYONE knows that that isn’t the only thing that happens when a batter attempts to bunt. That’s not a shock. We all know that the batter can reach base on a single or an error, he can strike out, hit into a force or DP, pop out, or even walk. We obviously have to know how often those things occur on a bunt attempt to have any chance to figure out whether a bunt might increase, decrease or not change the RE or WE, compared to hitting away. Why Palmer and Thorn or anyone else ever thought that looking at the RE or WE after something that occurs less than half the time on a bunt attempt (yeah, on the average an out and runner advance occurs around 47% of the time) could answer the question of whether a sac bunt might be a good play or not, is a mystery to me. Then again, there are probably plenty of stupid things we’re saying and doing now with respect to baseball analysis that we’ll be laughing or crying about in the future, so I don’t mean that literally.
What I am truly in disbelief about is that there are STILL saber-oriented writers and pundits who talk about the sac bunt attempt as if all that ever happens is an out and a runner advance. That’s indefensible. For cripes sake I wrote all about this in The Book 12 years ago. I have thoroughly debunked the idea that “bunts are bad because they considerably reduce the RE or WE.” They don’t. This is not controversial. It never was. It was kind of a, “Shit I don’t know why I didn’t realize that,” moment. If you still look at bunt attempts as an out and a runner advance instead of as an amalgam of all kinds of different results, you have no excuse. You are either profoundly ignorant, stubborn, or both. (I’ll give the casual fan a pass).
Anyway, without further ado, here is a summary of some of what I wrote in The Book 12 years ago about the sac bunt, and what I just obnoxiously tweeted in 36 or so separate tweets:
“Ok, you want numbers, here are numbers. From The Book. Based on 2000-2004 data (very high run environment). Runner on first, no outs, RE is .906. Runner on second 1 out, RE is .700. So a bunt looks like a terrible play. But that’s not the only thing that happens on a sac. In fact that happens less than 50% of the time. If we take all the results of a sac attempt and multiply their resultant RE by their frequency we get an RE of .831. That is .131 BETTER than an out and runner advance.
So, right off the bat, a sac bunt attempt is MUCH better overall than an out and runner advance. That’s because there are so many ROE and singles (which are of course partially balanced with bad results like an out and no runner advance.) But all together it is .836. Still not as good as the original .906 though. So a bunt ATTEMPT is still bad, right? Not so fast. The .906 is for all batters combined – the league average batter. Most bunts are attempted by weaker batters. The normal (no bunt) RE for a weak batter with a runner on first and no outs is closer to the mid .800’s. So right away you can see how the bunt attempt, on average, yields around the same RE as not bunting, AS IT SHOULD!
The reason it should is because the defense has a profound effect on the RE (and WE) of a bunt attempt (and hitting away to some extent). How can we tell?
Early in a game, the total RE for a bunt attempt is .886! Late in a game it is .783. That’s because early in the game the defense doesn’t play as aggressively as late in a game in a bunt situation. They shouldn’t. That’s because the bunt late in a close game doesn’t need as high an RE to be “correct” as early in a game. You already knew that. Playing for one run late in a close game is more important than early in a game, and a sac bunt attempt is definitely a “one run strategy” to some extent at least.
But that definitely does NOT mean that bunting early is rarely correct but bunting late is sometimes or often correct. Get that notion right out of your misguided head. It doesn’t make any difference. The defense takes that “late in the game edge” away by playing further in and reducing the RE of the bunt attempt. They ALWAYS make it so that hitting and bunting yield the same win expectancy (WE) whether it is the first or 9th inning, whether there are runners on 1st and 2nd or 1st or 2nd only. It never makes a difference. The defense controls the WE of the bunt attempt.
Why wouldn’t they? If either hitting away or bunting had a higher RE or WE than the other, the offense would always choose the option which yielded the higher value, right? But then, the defense could just play further in or further back to take away that advantage. The result is always an equilibrium where the WE from hitting and from bunting is exactly the same. There are two exceptions which I’ll get to in a few more paragraphs when I sum everything up. They will hopefully make perfect sense to you.
Remember I said that the RE in 2000-2004 for swinging away (actually swinging AND bunting) for an average hitter was .906. Again, some otherwise smart people would have you believe that a bunt attempt somehow magically results in an RE of .700 (a runner advance and 1 out). What do you think the average RE after a bunt attempt is with the best bunters, the ones who bunt for a hit alot? .907! They’ve already surpassed the RE for an average batter swinging away and these guys as a group are below average hitters! It is likely that the defense is playing all the way in against these guys and it is STILL correct for them to lay down the sac bunt 100% of the time! That’s because they reach base safely almost 30% of the time including walks and the times where they switch to hitting at 2 strikes. Whatever the numbers are, if you average all the RE’s of the various results of a bunt attempt, weighted by their frequency of occurrence, you get a total of .907 – not .700, the average RE for one out and a runner on second. A bunt attempt by a great bunter is much, much better than that. Even the worst bunters, believe it or not, early in the game, produce an RE of .867, also much, much better than this .700 “out and runner advance” fiction.
So here’s the deal: It’s the last time I’m going to write about this (maybe): For real good hitters who never bunt and never should, the defense plays all the way back. You know most of these guys (although you might be surprised at who could bunt and increase their RE/WE, given where the defense is playing) and you’ve seen the defense ignore the possibility of the bunt – rightfully so most of the time. In other words, if the batter were to lay down a bunt, even with the defense playing all the way back, on the average it would be worse than hitting away. There is no such thing as a surprise bunt being effective. If a so-called surprise bunt were effective – i.e. the resultant WE were higher than not bunting – the defense by definition would be playing incorrectly.
There are batters on the borderline of this group for whom this “we’ll play back and you’ll never bunt” dual (offense and defense) optimal strategy could change depending upon the circumstances of the game. If they do, then these batters would go into Group III which I’ll get to in a minute. (For the record, there is nothing the batter can or needs to do if that changes. The defense will be the one doing the changing – they’ll move up a little.) Anyway, that’s group I.
Group II are the fast and excellent bunters. The best ones. These are the guys who get that .907 RE even though the defense clearly knows they’re bunting. For them, the defense plays all the way in and it is STILL correct for them to bunt all the time. ALL. THE. TIME. Again, there is no such thing as a surprise hitting away. If that were correct – ever – the defense would be playing too far in. Again, there are some borderline batters in this category. Some of these at the lower end of the bunt quality spectrum move into the final category (the ones who are always in equilibrium and it doesn’t matter if they bunt or not) in certain situations where the defense should not be playing all the way in – if they did, the WE from the bunt would be less than that of hitting away.
Finally, there are all the others. Group III. These are players who can bunt pretty well and/or they are not good hitters and walkers. For these batters, the defense plays in exactly the position (depends on inning, score, runners, quality of defense, pitcher, park, weather, etc.) such that bunting and hitting away yield the same WE (RE is fine to use early in a game as a proxy for WE). It doesn’t make a damn bit of difference whether they bunt, hit or fart at the plate. Some of these batters, at the extreme ends of this group’s spectrum (the ones who are very good bunters but not good enough to bunt all the time even with the defense playing all the way up AND the ones who are good hitters and/or not good bunters, but not so much that they should hit away all the time with the defense playing all the way back), will also move into Group I or II at times, depending on the game situation.
To summarize, anyone who tells you that “bunting is bad” or “bunting is good” doesn’t understand bunting. They simply don’t know what they’re talking about. This is not controversial and it’s not my opinion. While the numbers I quoted are not hard and fast (although they are based on empirical data) and there is some slop in all of this (players and teams are sometimes out of equilibrium or adopt sub-optimal strategies for various reasons, although when they do, one or the other team is definitely exploitable), the basic idea is as true as anything else we have discovered about baseball in the last 30-odd years of analysis.”
MGL on Baseball 