One Statistic to Rule Them All: The ERA/Playoff Correlation

N MorrisContributor IFebruary 27, 2009

The fastest way to become a general manager is not as a jock; you are better off with an advanced degree in statistics. With the success of Theo Epstein in Boston and the recent hiring of Don Wakamatsu as the General Manager in Seattle, more today than ever before baseball teams want management with the ability to compress statistics. 

As teams rely more heavily on advanced measures of value, such as VoRP (Value over Replacement Player) and Range Factor, a statistic that is practically gray by comparison made a nice comeback in 2008: Earned Run Average.

It may not be as sexy as PFR (Power/Finesse Ratio), but few statistics told a better tale of making the 2008 playoffs than team ERA. As the adage goes, pitching wins championships, or at least gets you a chance to play for it.

Starting in the NL, the top four teams in ERA in 2008 were the Dodgers, Brewers, Cubs, and Phillies respectively. Remind me again what teams we watched in the National League Division Series? NL ERA was a better indicator of playoff teams than wins.

The AL ERA leader board is not quite as neat; the Blue Jays and A's ruined our fun, meaning you had to travel all the way to number six to see the final playoff team, the Chicago White Sox. Notably, Toronto’s offense was 11th in Runs scored in the American League, and Oakland was a dead-last 14th.

I know what you’re thinking. “Wow, teams that give up fewer runs win more than teams that give up more runs. This is groundbreaking stuff.” The key is that it almost didn’t matter how wretched your offense was, pitching alone was the key determinant.

If you had a top of the league ERA last year and even a middling offense, welcome to the 2008 MLB Playoffs! In the NL, you didn’t even need the middling offense (see Los Angeles Dodgers, 13th in NL in Runs).

Sadly, this doesn’t appear to be some secret statistical trend. 2008 is a small sample size. In 2007, only five playoffs teams were in the top five in their respective league ERA, with the Yankees and Rockies coming in about league average and the hard-hitting Phillies at 13th in the NL. 2006 saw six teams in their leagues’ top four in ERA, with the Yankees and Cardinals both average.

While ERA may not be the golden ticket to October that 2008 suggests, comparing these results to their offensive counterpart shows that we might be on to something. From 2006-2008, 17 playoff teams were in the top four in respective league ERA.

Over that same period, only 11 teams finished in their leagues’ top four in runs, and six of these finished in the top four in both pitching and offense. So of twenty-four teams to play in October the past three years, only five were able to get there on bats alone. Eleven (nearly half!) did it with just pitching.

Is there any logic behind the idea that good pitching is more valuable in the aggregate than equally good hitting? Sabermetricians think so. To score an extra run certainly gives your team a better chance of winning, but a better chance of winning comes if the other team scores one less run.

Need proof? I imagine that the winning percentage of teams who scored 15 runs in a game is astronomical. Almost off-the-charts high. Whatever it is, it isn’t as high as the winning percentage of teams who allow zero runs. The more runs you score, the more likely your team is to win, but the fewer runs you allow does the same thing and that one has a bottom.

Good pitching beats good hitting. Boston’s approach to pitching depth this year might be an indication that Theo Epstein agrees. By acquiring John Smoltz, Brad Penny, Takashi Saito and Ramon Ramirez, the Red Sox appear to have more pitching depth than any two teams outside of New England.

To hear it from a Red Sox fan, injuries to Ortiz and Lowell ended their 2008 season prematurely, but perhaps more important was an injured Shilling and a banged-up Josh Beckett.

While you watch the season unfold and the pennant races emerge this spring, keep an eye on the ERA column, just to see if 2009 shapes up like the last few years have. Pitching gets you to the playoffs. My apologies to the Texas Rangers.