F-Strike% (first pitch strike percentage): The percentage of plate appearances (for batters) or batters faced (for pitchers) that the first pitch was a strike. This includes anytime that the count after the first pitch was 0-1, or anytime the ball was put into play on the first pitch of a plate appearance.
Why you should care: Getting the first strike on a batter significantly decreases the batter’s chance of success and likewise increases a pitcher’s chance of success.
Current Baselines: The major league average F-Strike% for all players from 2005-2008 is 59%. There is very little variation in the major league average from year to year.
Batters: A lower F-Strike% is preferable for batters.
Pitchers: A higher F-Strike% is preferable for pitchers.