In the suggest-a-topic posts after Week 6 of the Baseball Prospectus Idol competition, “bravejason” asked one of the Idol contestants to explore the idea of whether swinging to protect the runner was a valid tactic. Before we can answer that question, we need to ask ourselves does swinging help the base stealer at all. This starts to open up an even more interesting discussion of what effect does the batter (if any) have on stolen base success rates.
Does Swinging Help the Base Runner?
I examined each stolen base attempt (removing those when a pitch wasn’t thrown, i.e., pick-off attempts) using Retrosheet play-by-play data from 2004 to 2008. I also filtered out all instances when the batter had two strikes as they are likely not to swing to protect the runner, and when they do swing they are simply protecting themselves.
Over those five years, these are the stolen base success rates when the batter does not swing versus when the batter swings.
Initially, it seems we have a counter-intuitive result: the batter swinging reduces the success rate. Obviously, the more likely scenario is that when the batter swings and misses, it is the result of a botched hit and run and not simple protection. In the hit and run situation, one either has a poor base stealer and/or a worse lead and slightly delayed start by the base runner.
To eliminate the first possible issue (a poor base stealer), I only considered situations where there was a prodigious (75 or more attempts over the five-year span) base stealer with a better than average success rate (77.0%). The difference reduces significantly, but still the counter-intuitive result holds:
It seems that there will be problems trying to tease out whether a batter swinging is actually helpful to the base stealer using this approach.
Does Swinging Affect Certain Catchers?
Another way to consider this is to find if certain catchers seem more affected by the batter swinging than not. For this, I looked at the 48 catchers who have attempted to throw out at least 100 base runners over the five year span from 2004 to 2008. The table below shows the top catchers who seem to be the most bothered by a batter swinging.
Catcher Doesn’t Batter
Swing Swings Difference
Chad Moeller 77.6% 93.3% +15.8%
Mike Napoli 73.5% 82.4% + 8.8%
Javier Lopez 85.7% 88.2% + 2.5%
Toby Hall 74.7% 76.5% + 1.8%
Chris Snyder 72.9% 72.2% - 0.7%
Joe Mauer* 61.8% 59.0% - 2.8%
* On a side note, one way to examine a catcher’s reputation is to examine the ratio of the number of stolen base attempts where the batter doesn’t swing to when the batter swings. Overall this ratio is 5.6 with a usual range for an individual catcher of 4.2 to 7.5. This suggests a level of how many times a team tries to advance a batter by a straight steal versus the hit and run. Joe Mauer is in a league by himself with a ratio of 2.8, i.e., teams realize that stealing on Mauer is so difficult that they rely much more on the hit and run for runner advancement.
The effect of the batter swinging was only statistically significant for Moeller, Napoli and Lopez. But here’s the important point. Given that the confidence level was 95%, we would expect from pure randomness 2.4 catchers out of 48 would be found to be statistically significant even if no effect existed. Therefore, only finding three catchers thought to be statistically significant is likely due to noise, and not due to any real signal.
So bravejason, it seems that swinging to protect the batter would be a bad tactic, as the evidence suggests that there is no consistent measurable benefit to the runner, and therefore the swing would simply be a wasted strike.
Handedness of the Batter
As a follow on, I was also interested in investigating the adages that having a left-handed batter benefits the base stealer when trying to swipe second, or having a right-handed batter improves the success rate of steal attempts at third.
The logic is that on an attempted steal of second base having a left-handed batter at the plate helps the base runner since most catchers are right-handed and the potential to bother the catcher’s throwing side will help. Unfortunately, there isn’t any evidence for this, as the success rate with a lefty batter is a mere 0.5% better. Harking back to presidential election polls and the classic “margin of error”, the margin of error on 11,462 stolen base attempts (with a success rate of ~77%) is 1.1%. This suggests there is no real difference between the handedness of the batter on attempted steals of second base.
Similarly, the notion of having a right-handed batter helping in the attempted steal of third base because he blocks the vision and throwing path of the catcher is unfounded as well as the success rate is essentially the same.