This morning, I was playing around with some of our plate discipline calculations. I really like the metrics we have for measuring a player’s approach at the plate, but because they are broad categories that combine numerous variables into one number, there are some questions that none of them answer all that well on their own. For instance, if you just wanted to know who the most unrepentant hacker in 2014 has been, you could simply sort the leaderboards by Swing%, and you’d see Chris Johnson at the very top, swinging at a higher rate of pitches (57.1%) than anyone else in baseball.
But knowing that Johnson has swung at the highest percentage of pitches doesn’t really make him the game’s most aggressive hitter, as part of his high swing rate is that he’s been thrown an above average number of strikes. Pablo Sandoval is right behind Johnson in overall swing rate, but his Zone% is 11 percentage points lower than Johnson’s, so he’s getting far fewer pitches to hit but still chasing the same amount. By any reasonable measure of hackiness, one would have to conclude that Sandoval has been more aggressive than Johnson.
Of course, we have a measure of swings at out-of-zone pitches, which is a pretty good way to measure which players fit the hacker mold. However, by O-Swing%, Matt Adams ranks #2 in baseball, but his overall swing rate only ranks 17th. Is he one of the game’s most deliberate free swingers, or does he just struggle to recognize balls from strikes?
When I think about the hacker label for a hitter, I think of guys who swing as if they had made up their mind before the pitcher even started his delivery. Location and pitch type are secondary to the desire to just put the bat on the ball, and they won’t be deterred from swinging no matter what the pitcher does. So, I thought that perhaps we could better identify those types of hitters by looking at a ratio of two of our plate discipline stats, and so out of curiosity, I divided Swing% by Zone% to get a ratio of swings-per-balls-in-the-zone. Others have created far more complex and mathematically sound formulas to get at the same idea, but there’s value in ease of calculation, so I was curious how Swings Per In-Zone Pitch would do.
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