Do Successful Steals Apply Measurable Pressure?

Consider the plight of the base stealer. In the 1980s, their role was sacrosanct. Get on base first, then cause havoc. For fans of speed and baserunning, it was a veritable golden age. Rickey Henderson and Vince Coleman each stole 100 bases in three separate seasons. Since 1980, the 13 top seasons in terms of stolen bases per plate appearance were 1980 through 1992.

Alas, the scurrilous forces of math and efficiency conspired to dethrone the stolen base. As it turns out, advancing one base is less good than creating an out is bad. It’s bad enough, in fact, that you need about three successful stolen bases to make up for the downside of getting caught once. The very best thieves managed that level of efficiency, but in aggregate, the league only crested a 70% success rate once from 1980 to 1992. Steals simply weren’t advancing teams’ goal of scoring as many runs as possible.

For a time, there was a reasonable counter-argument: what if attempting a stolen base has positive value that isn’t solely contained in reaching second base? Perhaps the pitcher has steals on the brain, or the defense loses its cohesion while attempting to cover the base for a throw. It doesn’t need to add much edge to make the math add up.

In 2007, the authors of The Book took up this question. They found a large advantage to batters when a runner was on first — exactly what proponents of steals suggested. There was a big problem, however. That advantage was for all runners on first base. The faster the runner, the smaller the advantage. In addition, actually attempting a steal carried a huge hit to the batter, more than enough to offset the advantage of having a runner on base.

Those results don’t tell you why steals hurt the batter, but it isn’t hard to come up with a theory. Batters alter their behavior on stolen base attempts — swinging less often to avoid fouling a pitch off if the runner has a good jump, for example. They also have to determine whether the runner has a good jump, and often see baserunners and fielders flash through their peripheral vision while they swing. When your normal job is to take your best possible swing, changes from your normal behavior can only be bad. Regardless of the reason, steals weren’t doing the disrupting that their greatest fans hoped for.

There’s still one final frontier that I haven’t seen discussed, though, one place that announcers and stolen base fans across the sport continue to advance. It’s that pressure! Pitchers crumble under the pressure of steals. Knowing that a runner just took the base from you — reached out and grabbed it by trickery rather than doing it with a double — surely weighs on the pitcher. Treating players like robots might make a stolen base seem worthless, but what about their feelings?

Well, yeah, those feelings sadly don’t account for much, as it turns out. To explore this question, I looked at every single play in baseball in the last three years that resulted in a runner standing on second and only on second. I broke those down into two categories: runners who reached second base via stealing it, and all other means of arriving there. That could be a double, advancing on a groundout, a wild pitch — anything other than a successful steal.

From there, I separated each category by the number of outs in the inning, then calculated how many runs scored in the remainder of the inning. For example, there were 6,227 instances of a runner reaching second base without stealing with no outs in the inning. In those 6,227 cases, an average of 1.162 runs scored in the remainder of the inning.

As an example, let’s use fan favorite Alejandro Kirk. On September 21, he led off the bottom of the fourth inning by doubling to left. The Blue Jays followed with a deluge of baserunners, scoring four runs in the inning to go from a 5-1 lead to a 9-1 cushion. In my accounting, that goes in as a four.

On September 22, fellow catcher Joey Bart followed a leadoff single by smashing a run-scoring double to deep center. The Giants, unfortunately, continued with three quick outs, which means zero runs scored after the double. The run that scored with the double doesn’t count, because we only care how many runs score after the game state of a runner on second base with no one out.

In this way, we can see whether it matters how the runner got to second base. Uh, nope:

Whether a runner reached second base by theft or other means didn’t give you any information about how many runs would score from that point on. That’s worse than it seems; runners who reach second via a successful steal are the kinds of runners who steal bases rather than the kinds of runners who are big-bodied catchers. Truly, if there were any pressure effect, you’d expect to see a marked increase in run-scoring in the stolen base case.

Of course, these conditions aren’t perfectly equal. We’re not doing a laboratory experiment here, alternately toggling the runners and batters in some kind of randomly selected double-blind setup. If we want to be rigorous, we need to account for the actual skillsets of the pitchers, hitters, and baserunners involved.

Luckily, I was able to do just that. In scraping every play, I also noted the identity of each baserunner, as well as the pitcher and batter for the subsequent plate appearance. Using this, I was able to compile averages in each state. For example, runners who reached second via a steal were good baserunners. Per 600 plate appearances, they were worth 1.5 runs above average according to UBR, our measure of baserunning value. Runners who reached second in any other way were almost exactly average baserunners — 0.02 runs above average per 600 plate appearances.

Next, let’s get to the interesting stuff. The average batter who stood at the plate after a steal of second was basically the average batter — a .320 wOBA. The batter who stood at the plate after any other advancement was marginally worse, though easily within the margin of error — they compiled a .319 wOBA. In other words, a batting talent disparity didn’t drive the results.

How about pitching? Pitchers on the mound after steals were, again, pretty close to league average. They allowed a .318 wOBA in aggregate. Pitchers who let runners reach in any other way were actually worse; they allowed a .321 wOBA in aggregate. This could still easily be noise, but if you’re looking for a reason why, consider that plenty of these pitchers, and none of the pitchers in the stolen base sample, had just allowed a double.

What does this mean in the aggregate? It doesn’t mean that stealing leads to better pitchers on the mound. It doesn’t mean that stealing makes you a better baserunner. These are merely selection effects. What it means is that there’s no evidence that a successful steal “puts pressure on the defense.” A successful steal of second base is great! It moves a runner from first to second. If you start giving it magical powers beyond that, however, you’re going too far, even if it feels like that steal should be worth something extra.