Tuesday, August 3, 2010

Spray Charts and Defensive Shifts

Here's my first look at plotting spray charts. I look at every batted ball in 2007-2009 of a few of the more famous pull-heavy left handed hitters, favorites for inducing defensive shifts. The cloud of hits obscures the baseball diamond behind it, but if you look closely, you can determine approximately where the infielders should ideally set up in order to pick up the most grounders:

I included Justin Morneau despite him not being a shift candidate because of an interesting study on batted ball distributions for "shifted" batters and non-shifted batters against trajectory angle of a groundball. Basically, what Jeremy found was that shifted LH batters have a higher BABIP when they hit opposite grounders toward the regular shortstop position, due to the absence of a shortstop because of the defensive shift. The non-shifted LH batters have higher BABIP up the middle and to the right.

He then made a model to predict BABIP with a defensive shift and without a defensive shift for several batters based on the batted ball distribution of grounders, average batted ball angle, and actual BABIP. Justin Morneau was found to be one of the hitters to benefit from a shift than without a shift.

My question (and possible future research idea) is, why not take the distribution of the batted ball angles for each hitter instead of the average? Some LH hitters (like Morneau) spread their grounders out much more than other LH hitters who are shifted do. But by nature of being a lefthanded hitter, Morneau's average batted ball angle is going to go towards the right of second base no matter the data, despite hitting the ball to the left and up the middle far more frequently than guys like Ryan Howard. The designated "shift" and "no shift" batters in order to create the BABIP on groundballs graph is a great idea, but is not perfect, as it also requires the researcher to select actual shift candidates.

Until defensive alignments on each at-bat are actually recorded (Baseball Info Solutions probably does, I'd have to check), I suppose that determining how a hitter would theoretically perform against a defensive shift will be an inexact science, especially when it depends on a groundballs model that is highly affected by the batter's foot speed. Still, definitely food for thought and awesome work by Jeremy.



Good work. Have to correct you, though. I did use the distribution and not the average. I agree that it would be crazy to use the average. And BIS tracks some defensive alignments, but I'm not sure if they track batter speed. FIELDf/x is what we really want.


BIS has been tracking batted ball timer data for the past two seasons now. If there's one way to estimate a batter's avg speed to first base, there it is. It should start an entire new wave of fielding assessment, at least until FIELDf/x gets here.

Anyway, just experimenting plotting charts straight from R. I've been having trouble fetching the 2010 PITCHf/x data though, so right now I only have the 2007-2009 seasons. I'll give another crack at it this week, but eventually might have to ask someone in the community to help me out.


One of the data files from Want Linux should cover 2010.

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