WPA/LI
Description:
Before you try and tackle Context Neutral Wins (WPA/LI), make sure you have a solid understanding of both WPA and LI. Got ‘em? Okay, cool.
So we know that WPA measures a player’s offensive contributions as measured by win expectancy, while leverage index measures the average leverage of all these situations. At the end of a game, not all players will have the same LI – some will have been in more pressure-filled situations than others – so how can we compare win expectancies between players? A player with a high leverage index may have a higher WPA simply because they were lucky enough to come up when the game was on the line and they could provide the most value.
With this in mind, if we divide WPA by LI, we’re seeing how much value a player provided regardless of the leverage. This number is called Context Neutral Wins (WPA/LI) because it neutralizes leverage while still measuring wins added (remember: 1 WPA = 100% win expectancy). WPA/LI is calculated over the course of a season for every at bat and is then summed at the end of the season to provide a player with their total WPA/LI. It is a good way to compare WPA between players.
Again, WPA/LI measures how much value a player provided to their team regardless of the leverage. Because of this, it is more a measure of a player’s talent level than WPA.
Context:
2010 WPA/LI Values
Things to Remember:
- WPA/LI allows us to compare WPA between players, but it still is not a predictive statistic. It’s a better measure of a player’s skill than WPA, but is still not as good as statistics like wOBA and WAR.
Links for Further Reading:
Get to Known: WPA/LI – FanGraphs
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