Get to Know: O-Swing%

O-Swing% (outside swing percentage): The percentage of pitches a batter swings at outside the strike zone.

Why you should care: When a batter swings at a pitch thrown outside the strike zone his chances of success are severely decreased. The ability of a batter to differentiate pitches inside or outside the strike zone is often referred to as plate discipline and O-Swing% is a good measure of true plate discipline. Likewise, pitchers try to get batters to swing at pitches outside the strike zone and O-Swing% for pitchers shows how adept a pitcher is at tricking batters to swing at pitches outside the strike zone.

Current Baselines
: The major league average O-Swing% changes slightly from year to year. The chart below shows the major league averages from 2005-2008 for both batters and pitchers.

2002          18.1%
2003          22.2%
2004          16.6%
2005          20.3%
2006          23.5%
2007          25.0%
2008          25.4%

Batters: A lower O-Swing% is preferable for batters.
Pitchers: A higher O-Swing% is preferable for pitchers.

Links and Resources:
Dissecting Plate Discipline: Part 1
Dissecting Plate Discipline: Part 2
More on Plate Discipline
Pitchers, Pitch by Pitch
Expanding the Strike Zone

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David Appelman is the creator of FanGraphs.

6 Responses to “Get to Know: O-Swing%”

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  1. robert j. says:

    Is there anyway to get a list of O-Swing% and F-Swing% for hitters and pitchers?

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  2. Jack S says:

    Something doesn’t look right there. League avg O Swing % jumped 26% between 2005 and 2008

    Could this be a pitch classification issue ? It just doesn’t seem right that league avg would move that much.

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  3. I’m guessing it’s a recording issue where perhaps BIS improved their pitch location gathering methods in 2006. If you look at a player’s O-Swing% above average I believe it will pretty steady from year to year, even taking 2005 into account.

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  4. Anais says:

    Perhaps the Plate Discipline numbers should all be presented relative to the league average rather than in absolute terms. If you look at Chipper Jones’ page and see that he has an O-Swing rate of 15.2%, it’s hard to know what that means, but expressed like OPS+ as 160 it’s very striking.

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  5. This is a great statistic to keep track of a batters discipline. In my opinion, any batter who tries to improve his O-Swing% will significantly increase their average.

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