What does xwOBA stand for in baseball?

Answered by Stephen Mosley

XwOBA stands for Expected Weighted On-base Average in baseball. It is a metric that measures a player’s offensive performance by taking into account the quality of their batted balls, such as exit velocity and launch angle, as well as their ability to reach base safely.

To fully understand xwOBA, it’s essential to break down the components that go into calculating this metric. Let’s start with the concept of on-base average (OBA). OBA represents the likelihood of a player getting on base, which is calculated by dividing the total number of times a player reaches base (hits, walks, hit by pitch) by their total plate appearances.

Weighted On-base Average (wOBA) takes OBA a step further by assigning different values to different outcomes. It considers that not all hits or walks are created equal. For example, a home run is more valuable than a single, so it receives a higher weight in the calculation. This helps provide a more accurate representation of a player’s offensive contributions.

Now, let’s focus on the “expected” aspect of xwOBA. The expected part comes from Statcast, a tracking technology used in baseball that records data on every pitch and batted ball. Statcast measures the exit velocity and launch angle of batted balls, which provide insights into the quality of contact a player makes.

By using this data, xwOBA calculates the expected outcome of each batted ball based on similar historical batted balls. This means that xwOBA considers the underlying quality of contact rather than just the actual outcome. For example, if a player hits a ball with a high exit velocity and optimal launch angle, but it is caught by an outfielder, xwOBA takes into account the expected outcome of that batted ball and adjusts the player’s xwOBA accordingly.

It’s important to note that xwOBA also incorporates Sprint Speed, a metric that measures a player’s running speed. Sprint Speed comes into play when evaluating certain types of batted balls, such as infield grounders or shallow fly balls, where a player’s speed can significantly impact their ability to reach base safely.

XwOBA is a metric that combines the principles of OBA and wOBA with the use of Statcast data to provide an expected measure of a player’s offensive performance. It takes into account factors such as exit velocity, launch angle, and Sprint Speed to evaluate the quality of a player’s contact and their ability to get on base. By utilizing this advanced metric, teams and analysts can gain deeper insights into a player’s offensive contributions beyond traditional statistics like batting average or OBA.