The Z Files: Is Average Exit Velocity on Groundballs Useful?
The Z Files: Is Average Exit Velocity on Groundballs Useful?

This article is part of our The Z Files series.

Increased use of advanced metrics for fantasy baseball analysis is obviously great. However, there's a downside. As more incorporate the data into their work, pressure mounts for others to follow suit. Unfortunately, the repercussion is not everyone fully understands the derivation and application of all that's out there, resulting in misuse.

A prime example of this is the expected Statcast stats, such as xBA (batting average), wSLG (slugging percentage) and xwOBA (weighted on base average). It's become commonplace to compare actual results to expected, looking for significant deltas. An actual stat higher than expected is often deemed lucky, and vice versa. On the surface, this makes sense. However, there's a major flaw in that reasoning.

Statcast deploys a unique means of measuring hit probability. In short, the components (exit velocity, launch angle, sprint speed, etc.) are compared to a database of similar batted ball outcomes and assigned a hit probability. What percentage of similarly batted balls are hits? What is the distribution in terms of single, double, triple and homer?

By means of example, if a specific batted ball was a hit 50 percent or the time, it counts as 0.5 hits and gets included in xBA as such. If it cleared the fence 10 percent of the time, it's logged at 0.1 HR and gets factored into xSLG, xwOBA etc, in that manner.

Missing from the above description is park influences. The same traits could be a homer 80 percent of the time in Yankee Stadium only to be

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ABOUT THE AUTHOR
Todd Zola
Todd has been writing about fantasy baseball since 1997. He won NL Tout Wars and Mixed LABR in 2016 as well as a multi-time league winner in the National Fantasy Baseball Championship. Todd is now setting his sights even higher: The Rotowire Staff League. Lord Zola, as he's known in the industry, won the 2013 FSWA Fantasy Baseball Article of the Year award and was named the 2017 FSWA Fantasy Baseball Writer of the Year. Todd is a five-time FSWA awards finalist.
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