It was Billy Beane in Moneyball who famously remarked, “The playoffs are a crapshoot”. The argument goes that whatever assiduousness and craft goes into producing a winning regular season team, the outcome of the playoffs is random. I want to use my offseason opportunity this year to explore this a little bit. A warning up front: there will be a fair amount of math, and I’m not going to come close to explaining it all. But I give a few references, and I’ll try and answer any questions you have.
Stating the Obvious
We need to start by clearing away some underbrush. The first (and I hope obvious) point is that no team has ever won the World Series without making the playoffs. So the teams from which the World Series champion emerges are all pretty good teams… certainly none of them is putrid. The collective season won-loss records of the teams in the playoffs this year was over 60% but the collective records in the playoffs will be exactly 50%, so on average, every team plays worse than they played in the regular season. The average quality of opponents faced will inevitably be higher than the average quality of opponents faced in the regular season, so the expected winning percentage will be lower.
Second, every baseball game ever played has some combination of luck and skill. Most people don’t think about what this really means, and even when they do, they greatly overemphasize the relative effect of skill, as I hope I’ll demonstrate in the next installment. But there is one fact about luck that needs to be remembered: it evens out over the long run but can dominate results in the short run. Since the playoffs are shorter than the regular season, whatever component luck plays in an individual game will have a higher relative impact in the playoffs. If they played, say, a 31 out of 60 series, instead of 3 out of 5 and 4 out of 7 series, more skillful teams would almost always win. But they don’t.
This evening out of luck in the long run is not some huge surprise to baseball fans, for whom the phrase “small sample size” requires an acronym just to avoid tedious typing. But quantifying it is what will take some math. Some of the math to do so actually originates in sabermetrics, from Tom Tango.
Third, this result is independent of changes made to teams to better prepare them for the playoffs and to changes in managing strategy in the playoffs. In any given series, both teams make these changes, so they don’t affect the relative effect of skill very much at all.
Finally, not only is luck of higher relative importance in the postseason, just because there are fewer games, but our estimates of team’s skill going into the playoffs is overestimated for the good teams by the excess of luck they happened to have in the regular season – this is the phenomenon known as regression to the mean, and it is invoked six times more often than it is understood.
Sum of its Parts
These three factors: better quality opponents, shortened playoff seasons and regression to the mean all serve to flatten results: they reduce the chance that the best teams will win the World Series. I don’t mean to suggest that there may not be other factors, but in this series I’ll try and quantify these three. It is not my goal to subtract from the romance of baseball, as one is often accused of doing by sneaking math into the discussion. On the other hand, though, the following xkcd cartoon pretty much defines my whole working life, as well as idle sports conversation in bars (no comment on how different that is from my working life):
If you don’t want to read the rest of the series, I forgive you, and I’ll cut to the chase: it’s pretty much a crapshoot. To be precise, it’s about 90 percent crapshoot and 10 percent skill. Billy Beane is right.
Thanks for reading The Playoffs are a Crapshoot!
Long live Braves Journal
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