Predicting win-loss records

Baseball is very simple, right? The main premise is to score more runs than the other team, while simultaneously keeping them from scoring runs. By making that statement, it is implied that you should be able to look at the number of runs scored and runs allowed by a team and determine their win-loss record. That is true for the most part, but there is enough differentiation with actual application that Bill James created a formula, called the Pythagorean Win-Loss, to estimate how many games a team SHOULD have won based on the number of runs they scored and allowed.

This formula can be used to determine which teams have more “luck” than others, but it does not explicitly determine skill and talent level of teams. Simply put, the formula can be used to look at the relationship between runs scored and allowed and project a win-loss record.

The first order win percentage in the charts below show the Pythagorean win-loss for each team. You can see that many teams outperform, or underperform, their predicted win-loss record. These standings look much different from the actual standings. The Red Sox would be a wild card team if they had performed up to their expected.

You can compare the actual win percentage with a team’s first order win percentage. The numbers on the right of the table show the difference between the actual win percentage and the Pythagorean win percentages. Numbers in the red indicate teams underperforming compared to their expected win-percentage. The Astros have the worst record in baseball, but if it is any solace to Astros fans, they should have about 4 more wins.

Here’s the link to the most recent Adjusted standings. The table above shows the Pythagorean records as of August 9th, courtesy of Baseball Prospectus. The second and third order win percentages expand on the formula above, and includes more data such as opponent quality and other statistics that predict how many runs a team SHOULD HAVE scored. 

The most extreme example of a team over performing their Pythag is the Orioles. They have won almost 10 more games than their adjusted win-loss predicted. They are having a great season, but it seems they may have benefitted from some “luck” than other teams. The season is very long, and there is plenty of time left for the Orioles to prove they are legit. 

Its interesting to track the Pythagorean adjusted standings because they can fluctuate wildly game-by-game. If there is a blowout in one of tonight’s games, the standings will change greatly. But for now, enjoy playing the what-if game for baseball fans.