The Red Sox put themselves behind the eight-ball by dropping the first three games to the Yanks in the 2004 ALCS. Going into the series it looked like a very good match-up between two equally talented teams. The Bosox losses are a definite surprise. Based on probability and the assumption of equally matched teams, the Yankees only had a 12.5% chance of winning all of the first three games. (The chance of winning any game between equally matched teams is 50%, making the probability of three wins in a row .5 x .5 x .5 = .125). But now, the Red Sox chances are only 6.25% to come back and win the series.
Based on history, however, the chances of a comeback are worse than probability would suggest. In 25 previous best-of-seven MLB playoff series where one team went up 3-0, the losing team has never come back. In fact, they've been swept in four games 20 times. Two things are at work here:
- Based on having lost the first three games in the series, it's logical to assume that the teams were not equally matched in the first place. The chances of coming back drop well below 6% if your chance of winning one game falls below 50%.
- The demoralizing nature of having lost the first three kicks in making future wins less likely.