Another season is in the books, and it was a great one. Between the late-season heroics of CC Sabathia and Johan Santana, the demise of the New York Yankees, and the historic run by the Tampa Bay Rays, the 2008 season brought plenty of drama and good memories. And though the World Series only lasted five games, the last of which was rained out twice, it was still a great match-up, between a young Rays squad that had never even been to the postseason and a more experienced Phillies team that was looking to bring back the world championship to Philadelphia for the first time in 28 long years.
The Phillies won, and though I wouldn’t, some might attribute that victory to experience. After all, how many times have we heard that experience wins in the playoffs? But is that true? Let’s find out.
Here’s my methodology. First, I calculated for each player the amount of times he had been in the playoffs up to a certain point in his career. So the first time Derek Jeter went to the postseason, in 1996, he had zero years of playoff experience, the next year he had one, and so forth.
Next, for each postseason team, I calculated how much experience it had, weighted by each player’s playing time in that series. So for example, the 1996 New York Yankees had 228 plate appearances in the World Series. Wade Boggs had 12 of those, and four years of playoff experience. Therefore, he added 12/228*4 = 0.21 years of playoff experience to the roster. Overall, the Yankees hitters in the World Series that year averaged 1.59 years of previous postseason experience.
I went through the same process with pitchers, weighting their experience by innings pitched. Finally, I average out the numbers for hitters and pitchers to arrive at a final number. The most experienced team in playoff history turns out to be the 2007 Yankees, with an average of 5.23 years of prior postseason experience, while least experienced teams, 14 in all, had a grand total of zero years of postseason experience. Most of those teams come from the early days of baseball, but the 1961 Reds make it onto that list, too.
One thing we can do is look at the experience gap between the winners and losers of each playoff series, ever. It turns out that the average winning team has 0.12 more years of experience than its opponent, and that the more experienced team wins 54.2 percent of the time. That’s interesting, but it’s tough to tell how significant it is.
What we need is a finer statistical tool, namely regression. In my regression, I included every seven-game series played since the end of World War II, 105 in all, and calculated for each the difference between the teams’ Pythagorean winning percentages and the difference in their experience level. I then asked the regression to predict whether a team won or lost based on those two variables.
The relationship between Pythagorean record and a team’s odds of winning a series were, as expected, positive. For every extra win in the regular season that a team had on its opponent, its odds of winning the series rose by about 0.36 percent. In other words, if a 95-win team faces an 85-win team in a seven-game series, its odds of winning the series are around 53.6 percent. That’s a small difference, and the coefficient is actually not statistically significant, suggesting that there is not much of a relationship between a team’s record and its odds of winning a playoff series. I only kept the coefficient in my regression because its sign did at least point in the right direction, that is, that the better team is more likely to win a playoff series.
But while a team’s record did not have much of an effect on its odds of winning a postseason series, its advantage in experience did. A team that had, on average, one more year worth of postseason experience than its counterpart, is expected to win their post-season series 54.2 percent of the time, which is nothing to scoff at. The result was statistically significant at the 10 percent level.
Given that one standard deviation in experience difference was 1.5 years, that means that about one-third of all series will see one team favored to win 56.3 percent of the time due solely to its superiority in terms of postseason experience, and 5 percent of the time, a team will start out with a 62.1 percent chance just due to its playoff experience edge.
This is a pretty huge result, and a victory for traditional baseball thinking. It looks like previous postseason experience does help a team win in the playoffs after all.