February 17, 2011

Spitballing

Always in Motion is the Future?

by Jeremy Greenhouse

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“The phrase 'off with the crack of the bat,' while romantic, is really meaningless, since the outfielder should be in motion long before he hears the sound of the ball meeting the bat.”–Joe DiMaggio

Before each pitch, a fielder wants to position himself such that a batter will be no better off making any adjustments to his approach.  Nevertheless, at last year’s PITCHf/x summit, Max Marchi used FIELDf/x data to verify DiMaggio’s assertion that fielders are in motion before the ball is put in play. So what informs a fielder’s first step?

Jonathan Hale has studied the spray angle of batted balls by pitch location. Unfortunately, only a month’s worth of HITf/x data has been made publicly available. Furthermore, hit location data can at times be shaky. But one objective way to tell where a batter is likely to hit a ball is by marking the player who fielded each ball. Combining that data with PITCHf/x plate location data provides insight into what a fielder can expect when he hears the crack of the bat.

For outfielders like DiMaggio, the horizontal location of a pitch is a great visual clue. The following graph presents the probability of a left, center, and right fielder retrieving a ball based on its horizontal pitch location:

50% of balls in play are claimed by outfielders. The likeliest outfielder to field a ball corresponds with the side of the plate to which the ball is pitched. A ball pitched on the third-base third of the plate is much more likely to go to the left fielder than to the right fielder, and vice versa.

Most batters hit fly balls to all fields, while pulling a majority of ground balls. Batters are less likely to hook a grounder the further away the pitch is from them. When jammed inside, nearly a quarter of balls in play are pulled to a corner infielder:

The height of the pitch matters as well, but more for purposes of batted-ball trajectory than location. A pitch hit at the bottom of the zone has a 60% chance of finding an infielder, whereas most batters are able to get pitches in the top half of the zone into the outfield. Interestingly, the trend reverses at a certain point around the letters, where batters are more likely to pop the ball up or chop it into the ground than drive it into the outfield:

Finally, different batters pitched in different spots hit to different fields. No batter seems to “aim” the ball quite like Ichiro, so I decided to use him as my example. Ichiro tends to go the other way when pitched high and outside. He goes up the middle to center field when pitched down in the zone. On pitches down and in, he pulls grounders, and he notably hits grounders to left field on pitches up and in. Below I show the fielder most likely to retrieve an Ichiro batted ball based on its pitch location:

Perhaps this line of research falls under the category of fielder instincts. Optimal positioning prior to a pitch can only go so far, as a fielder should be taking in new information constantly, be it a gust of wind, the batter's stride, or the pitch location. However, that first step can be the difference between a ball being fielded on the bounce and fielded for an out. Most of these insights a fielder already understands through years of experience and repetition, but intuition isn't worth much when it's not backed up by data.

Jeremy Greenhouse is an author of Baseball Prospectus. 
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