December 23, 2007

BUT YOU BETTER HAVE A FASTBALL...:

Fastball, slider, changeup, curveball—an analysis (John Walsh, December 20, 2007, Hardball Times)

These numbers confirm (and quantify) what we already knew: pitchers tend to throw more sliders and curves and fewer changeups, when they have the platoon advantage (pitcher and hitter of the same hand). In any case, pitchers throw a majority of fastballs (59% of pitches thrown) no matter what side of the plate the batter is standing on.

We can also look at how pitch selection varies depending on the count:

+------+------+------+------+------+
| Cnt | FB% | SL% | CB% | CU% |
+------+------+------+------+------+
| 3-0 | 0.84 | 0.05 | 0.03 | 0.08 |
| 3-1 | 0.80 | 0.10 | 0.03 | 0.07 |
| 2-0 | 0.75 | 0.11 | 0.04 | 0.10 |
| 3-2 | 0.66 | 0.17 | 0.08 | 0.09 |
| 1-0 | 0.63 | 0.15 | 0.08 | 0.13 |
| 2-1 | 0.64 | 0.16 | 0.08 | 0.13 |
| 0-0 | 0.63 | 0.15 | 0.12 | 0.09 |
| 1-1 | 0.53 | 0.19 | 0.13 | 0.14 |
| 0-1 | 0.52 | 0.20 | 0.15 | 0.12 |
| 2-2 | 0.51 | 0.21 | 0.16 | 0.12 |
| 1-2 | 0.48 | 0.22 | 0.19 | 0.11 |
| 0-2 | 0.51 | 0.21 | 0.18 | 0.09 |
+------+------+------+------+------+

I've placed the rows in this table in order of how advantageous the count is for the hitter, 3-0 being the best hitter's count and 0-2 being the worst. Now look at the fastball percentage: there is an almost perfect progression from lots of fastballs (84% on 3-0) down to about 50% fastballs on the worst hitter's counts.

What's clearly happening is that when behind in the count pitchers will try to throw a strike to move the count in their favor. Presumably, the fastball is the easiest pitch to control, so that's the pitch they choose. When they are ahead in the count, the cost of throwing a ball is reduced, so they can try the fancy stuff.

A possible exception may be given by the 0-2 count, where the fastball percentage goes back up a tick, instead of continuing downward. I wonder if pitchers are employing a little game theory here: throwing a few more fastballs than expected in order to confound the batter.

Now that we have some idea about pitch selection, let's have a look at what happens to these different pitches. [...]

I don't know about you, but I've learned a lot researching this article. I didn't realize the averge fastball was thrown comfortably above 90 mph. I can remember, not all that long ago, when 90 mph was considered throwing hard; now it's below average.

The changeup, despite was you sometimes read, is not the slowest pitch thrown (the curveball is). I read recently a claim that somebody's changeup was 20 mph slower than his fastball—no way! The average difference between fastball and changeup is 9 mph. I haven't checked, but I'm confident that nobody has a 20 mph difference between the two pitches.

Pitchers throw the changeup three times more often when facing an opposite-hand batter, but throw the fastball equally as often, regardless of the handedness of the batter. This is not a good stategy, as you will see when you read my article on platoon splits for different pitch types in the Hardball Times Basebll Annual 2008 (plug!).

Fastballs appear to have the worst BABIP and sliders the best, although a rigorous link between BABIP and pitch type needs more study.

Posted by Orrin Judd at December 23, 2007 9:39 AM
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