Run Differential: “Big Diff”?

“Big diff”. Remember when people used to say that? People used to talk so cray back in the day.

On to the subject at hand, run differential. As you may know, because you’ve seen it tweeted, re-tweeted, or written about countless times in the 2012 baseball season, the Texas Rangers are really good at run differential. In fact, they’re better than all other teams at run differential. They’re even almost better than all other AL teams with a positive run differential combined. If you don’t know, run differential is very simply derived by subtracting the runs scored against a team from the runs scored for a team. In short and sweet terms, you have a high (good) run differential if you score a lot and don’t give up very many runs. The Rangers score a lot (#1 in MLB), and don’t give up very many runs (tied for #4 in MLB). 

So what is the big deal about run differential, and why are so many pointing to it as evidence of a team’s strength? At a basic level, the obvious answer is that the team’s that are good at scoring runs and not giving up runs are the best teams, since that is the object of the game. At a deeper level, run differential can be used to mathematically put into perspective a team’s abilities, independent from just their win-loss record. There is a sabermetric term called “Pythagorean Winning Percentage”, or a team’s “Pythagorean record”. You can read in more detail about it here. In short, the Pythagorean Winning Percentage is a formula that uses a team’s runs scored and runs against to attempt to provide a more accurate expected win total for the season than using only a team’s basic win percentage.

Now let us put that into practice. The Rangers are currently 31-18, for a .633 win percentage. Over a 162-game season, a .633 win percentage would translate to a 103-59 record. On the other hand, the Rangers Pythagorean Winning Percentage is currently .705, which would translate to a final record of 114-48. Basically, what this tells us is that the Rangers are really, really good – even better than their current record. However, if we use the same method on the Los Angeles Dodgers (currently with the best record in baseball), we receive different results. The Dodgers are 32-16, with a .667 win percentage that would translate to a 108-54 record over a full season. Their Pythagorean Winning Percentage for the Dodgers is currently just .623, or the equivalent of a 101-61 record for their 2012 season. As you can see, despite the Dodgers holding the better record today, the Pythagorean method tells us that we can expect the Rangers to end the season with as many as 13 more wins than Los Angeles.

Now for the real question: does this really matter? If we review the last 10 years of MLB history, from 2002-2011, the league leaders in run differential have seen their regular season end thusly: Wild Card, Division Winner, Division Winner, Division Winner, Division Winner, Division Winner, Division Winner, Division Winner, Wild Card, and Division Winner. That is eight division winners and two wild cards, a perfect ten out of ten playoff berths. So in that regard, run differential appears to be a clear indicator of playoff-bound teams.

However, once the playoffs begin, any sign of correlation between regular season run differential and postseason success gets a little hazier. Those same run differential leaders saw their playoffs run end like this: World Series Champion, Division Round Loser, World Series Loser, League Championship Loser, Division Round Loser, World Series Champion, Division Round Loser, League Championship Loser, League Championship Loser, Division Round Loser. That boils down to four 1st round losers, three 2nd round losers, three World Series teams, and two World Series Champions.

Conversely, the World Series champions from the last 10 years finished the regular season with the following ranks in run differential: 1st, 11th, 2nd, 5th, 15th, 1st, 3rd, 2nd, 4th, and 8th. Each of the World Series Champions had a positive run differential, but the 2006 Cardinals came dangerously close to crossing negative with just a +19 run differential, yet still went on to become the champions.

When you boil it all down, run differential tells us things that we should already know. It clearly divides the good teams from the bad teams. It gives us an idea of which teams are over-performing, under-performing, or performing in line with expectations. It also is only truly a good indicator of a team’s strength during the regular season, which confirms the old adage that playoff baseball is different than regular season baseball. In 2012, it also tells us that the Rangers are the best team in baseball. Most spectators of the sport ought to be able to tell you these things without knowing the formula for Pythagorean Winning Percentage.

There are no trophies for having the best run differential in baseball. At the end of the season, run differential doesn’t matter. All that matters is wins and losses, making the playoffs, and then what you do in the playoffs. A team’s run differential isn’t going to do any of those things. All that run differential can do is give us a little more comprehensive view of just how good a team has been.

As much as I would like it to, a math equation will never be able to predict with absolute certainty the results of a baseball season. There are many factors that do not fall into any equation, nor could they ever, such as injuries, luck, or randomness. Correct math is never wrong, although sometimes it is limited. I would advocate using one’s eyes and one’s calculator in cooperation, allowing the one to test the other in order to come to the most complete conclusion. To bypass the use of one will only limit the other, and do an injustice to the overall goal you first sought to accomplish.

Peter Ellwood is a Senior Staff Writer for Shutdown Inning. You can email him at or reach him on Twitter @Peter_Ellwood
Peter Ellwood

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