How Often Do the Best Regular Season Baseball Teams Win It All?
The Red Sox finished the regular season with 97 wins, the most in the American League, matched only by the St. Louis Cardinals. This should portend good things for their playoff run, right? Well, if history is any guide, going into the playoffs with the best record in baseball doesn’t much improve a team’s odds.
While 162 games provides a pretty substantial sample size for determining the best team in baseball, the playoffs are a brutal, luck-driven set of five- and seven-game series—assuming you’re lucky enough to avoid the new wildcard format—that overwrite what six months of continuous competition have more fairly demonstrated. Still, there are indicators that might hint at the Red Sox’s postseason chances.
It can’t hurt to enter the playoffs with not only the best record in the Majors, but the best run differential—or the number of runs a team has scored against the number of runs it has allowed, a stat that provides the basis for Bill James’s Pythagorean Theorem—and the league’s highest OPS (on-base percentage plus slugging percentage) to boot.
Unfortunately, those metrics of evaluating success don’t offer much promise for Boston’s playoff odds. Since the Major League Baseball playoff system expanded in 1995 to include a divisional round series, the team or teams with the best record in the regular season have won the World Series just three times. Three World Series winners in 18 years is, at first glance, slightly higher than the expected average of 2.25. But because there have been multiple years like 2013 when two teams have shared the best record, the number is actually lower than three. Thus, over the past 18 seasons, the team with the best winning percentage has been about as likely to win the World Series as a playoff qualifier selected at random.
Looking at another metric, the Red Sox are the 45th team since the 1995 season to win at least 97 games. Of the 44 teams that have previously eclipsed the 97-win mark, only seven won the World Series. Of course, there are cases where, because a 97-win team won the World Series one or more other 97-win teams could not, but the mean number of series won by 97-plus-win teams is exactly one; on average teams with similar or better records than the Red Sox beat their Divisional round opponent, but lost in the Championship series.
While 97 is a fairly arbitrary win total, the data suggests that although the Red Sox won five more games than the Tampa Bay Rays, they are far from locks to advance beyond the first round. 97-plus-win teams are 24-20 in the Divisional Series.
If any number portends good news for the Sox, it’s the run differential where three of the 18 league-leaders since 1995 have gone on to win the World Series. Unlike the win-loss record, there has been just one unique team with the best run differential each season. So we can conclude that over that span, run differential has produced more World Series winners than the expected average, 2.25.
Further, all three of those World-Series-winning teams had exceptional scoring advantages over their opponents, as the Red Sox did in 2013. In fact, only 13 teams since 1995 have had run differentials greater than Boston’s +197 this season. Three of those teams accomplished that feat en route to winning the World Series. The issue with drawing happy conclusions here, which has been constant throughout, but is most glaring now, is the minuscule sample size. It is impossible to make confident claims of a pattern when your sample size is less than 20. It is encouraging that the limited data supports our preconceived hypothesis—that teams with the exceedingly great regular season run differentials are more likely to succeed in the playoffs—but it can only support what amounts to a theory.
So then, ultimately, there’s little comfort in entering the season with stats as strong as those of the Sox. 162 games brought order and stability and a fair representation of how teams have performed. But prepare yourselves Red Sox fans, for the playoffs are dark and full of terrors.