Anatomy of a player: league average pitcher Part 2

It has been far too long since I posted part 1 of the league average pitcher series, which looked at league average numbers for fastballs. Now, finally, we will tackle breaking balls. As with fastballs, we will find the average speed and movement for each type of breaking ball, but we also will go a little deeper and look at the difference in speed and movement between breaking balls and fastballs. This will give us some idea of life as a major league hitter and what he has to deal with.

This article will deal with curves, sliders and change-ups, but won’t talk about split-finger fastballs. First, not a lot of pitchers use the split-finger fastball and second, my classification algorithm is at its worst identifying split-fingers.

As in the previous article, when I say horizontal movement, that means how much a ball moved horizontally compared to a ball thrown without any spin. Negative horizontal movement is a ball that moves in to a right-handed batter. All pitches thrown by a left-handed pitcher have been multiplied by -1 to get horizontal movement (essentially flipping the pitch or looking at it in a mirror) so all pitchers are on equal footing. Negative vertical movement is down. All movement will be measured in inches and all speeds will be measured in miles per hour.

I won’t show any histograms breaking down individual types of pitches as in the previous article because these are basically the same as previous histograms. What I am going to show instead will be tables with all of the final information put together.

So, starting with the raw averages.

Type       Speed (mph)  Hor. movement (in.)  Vert. movement (in.)
Curve          77.3           4.7               -4.4
Slider         83.3           2.3                2.5
Change         82.5          -6.5                5.8

As expected, the curveball is the slowest of all the pitches and it is the only pitch that drops more than a pitch thrown without spin. The horizontal movement of the curve is positive, which means it moves in the opposite direction of the handedness of the pitcher. If a pitcher were to throw a curveball in a perfect 12-to-six motion, it would not have any horizontal movement, just vertical movement. As the pitcher’s arm angle drops, the ball is imparted with more and more horizontal movement and less vertical movement. Because the magnitude of the horizontal movement is just as large as the vertical movement, this gives us a clue that the majority of pitchers in the majors aren’t throwing 12 to six.

Sliders are kind of in between cutters and curves, and the speed and movement bears this out. The speed and movement are almost an average between the curve and cutter (88 mph: 0.0 horizontal 6.6 vertical). The variance of sliders, though, is larger than any other pitch because sliders can come in several different varieties. Hard sliders tend to be faster than average, with less horizontal movement and move vertical movement. On the slider spectrum they are closer to cutters than curves. On the other end of the spectrum you have slurves, which are closer to curve balls and are slow with more horizontal movement and less vertical movement. I hope that as the data pile up, sliders will be broken down further into categories like these.

Change-ups are fastballs in disguise. They are meant to move like a fastball, but are thrown much more slowly than fastballs. This speed difference is what makes the pitch effective. We can get a better idea by looking at the difference between these breaking balls and fastballs. To do this, I assign whatever is the most-thrown fastball by a pitcher and then calculate the difference between each of his breaking balls and that fastball. Averaging each pitcher, we come up with the next table.

Difference between fastball and breaking ball

Type       Speed (mph)  Hor. movement (in.)  Vert. movement (in.)
Curve          -11.7         -9.2               -12.9
Slider         -7.9          -6.4               -6.7
Change         -9.8           1.1                2.8

All the speeds are now negative because all breaking pitches are slower than the fastball. While curves still are the slowest, changes appear closer in the difference because few pitchers who throw hard also throw devastating curve balls. Conversely, many “crafty veterans” who have lost a little on their fastballs throw more curves. Here you can see what a huge difference there is between a fastball and a curve ball, with more than a foot difference in vertical movement. If you guess fastball and get a curve, you are going to look silly.

Sliders are slightly toned down from the large difference. Partly, this is due to sliders being kind of a hybrid between curves and cutters, but a lot of “sinker-slider” pitchers throw sinking fastballs and complement that with a slider. These pitches tend to have very similar vertical movement, but opposite horizontal movement.

And finally, we can see the true beauty of the change-up. It has incredibly similar movement to a fastball, but is thrown almost 10 mph more slowly. While the pitch can appear to have the bottom drop out of it, that isn’t because of the spin on the pitch. It is due to the speed. Because the ball is traveling more slowly, gravity has more time to act on it, making it appear to drop more than a fastball, but the movement because of spin is almost identical. So if the hitter is looking at the rotation of the ball hoping to pick up a clue as to what the pitcher has thrown, he still will be fooled by a well thrown change- up.

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