THT: Walsh: How fast should a fastball be?

“Which is the better pitch: an 87-mph fastball on the outside corner or 96 down the middle? John has a look using (of course) PITCHf/x.”

The first plot shows the percentage of swing-and-misses relative to the number of swings. We expect a greater percentage of misses as speed increases and we see that for both the low-and-away and the middle-in pitches. The trends aren’t that startling, although it appears that throwing above 94-mph really helps, especially on the inside pitches. Naturally, pitches on the outside portion of the plate are harder to hit than inside pitches. In any case, there is nothing in this plot that explains why speed doesn’t matter low-and-away.

Next, we have the percentage of called balls, relative to the number of taken pitches. I found this plot fascinating, mostly because it came as a surprise. Around 30 percent of all taken pitches in the low-and-away zone are called balls and the faster the pitch, the higher chance it has of being called a ball. Remember, essentially all these pitches are actually in the strike zone and should have been called strikes. So, here we see a definite disadvantage to throwing hard—you have a greater chance of a bad call from the umpire. That sucks doesn’t it? Ninety-eight mph heater at the knees on the outside black: BALL! calls the ump. Same exact location, but now it’s thrown at 86 mph: STRIKE! Maybe this is the reason that guys like Tom Glavine, who work the outside corner with soft stuff, seem to get more than their share of close calls.