Several weeks ago, I suggested that one of the reasons Adam Eaton may have had a hard time getting even a team of little leaguers to make outs was because his curveball was a little flat, particularly when compared to the trajectory of his fastball.
My theory was based on plots displaying the amount of vertical and horizontal break of Eaton's pitches over the course of the 2007 season.
A few readers pointed out that according to the plots, there appeared to be approximately a 10-inch difference between the vertical breaks of Eaton's fastball and curveball, seemingly a significant and typically effective disparity.
Good point. Required further digging.
First, I looked at players that have the reputation of a pretty good curveball. Brett Myers is one such player.
Eyeballing Myers graphs suggest a 17-inch to 19-inch difference in the vertical break of his fastball and curveball. That's quite a bit more than Eaton's ten-inch difference. But then again, Myers has a pretty exceptional curveball, so perhaps it's not fair to compare Eaton to him.
Below is the vertical break, expressed in inches, of Eaton's fastball and curveball, compared to the MLB average.
FB Curve Diff(in) Eaton 9.2 -1.6 10.8
MLB Avg 8.9 -3.3 12.2
And here's the horizontal and vertical breaks of Eaton's curveball versus the MLB averages.
Vert. Horiz
Eaton -1.6 4.9
MLB Avg -3.3 5.2
Diff(in) 1.7 0.3
It's pretty clear that Eaton's curveball breaks less than the league average, both horizontally and vertically. Now, whether this makes a difference or not is hard to know, but, when you consider that his curveball breaks only half as much as the league average's, well, it doesn't bode well.
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Thanks go out to Josh Kalk and The Hardball Times for the use of the Pitch f/x data.
