According to Baseball Reference data, since the World Series began in 1903 there have been 1,414 postseason games and 147 (10.4 percent) have gone into extra innings. Postseason games have been 9.22 innings on average with a standard deviation of 0.79. Which would put this weekend's game 11.11 standard deviations from the mean.
But the modern playoff format, with both division and championship series, didn't really begin until 1995. Since 1995 there have been 636 playoff games with 70 (11.0 percent) going into extra innings. Eleven of the 13 longest playoff games have come since this reformatting. Since 1995, playoff games have been slightly longer at 9.28 innings on average with a standard deviation of 0.96. That puts this weekend's 18-inning game at 9.10 standard deviations from the mean. Which is still incredibly unlikely.
Above is a histogram showing how the frequency of lengths of all extra-inning playoff games since 1903. Among the 10.4 percent of playoff games that go into extra-innings, 91.2 percent end by the 12th inning. Only 1.4 percent (two games) have made it to 18 innings.
To give you an idea of how improbable that is, here are some other things 9.10 standard deviations from the mean.
- An NFL player rushing for 229.3 yards per game (2013 data, min. 100 attempts)
- An NBA team getting beat by 83.0 points (2013-2014 data)
- An 18- to 65-year-old American male who weighs 570.6 pounds (EPA NHANES IV data)
- A 13.4 inch penis (LifeStyles condom data)
Chart by Sam Woolley
Photo: Patrick Smith / Getty Images Sport