Gopher Balls

On Thursday I took a look at Johan Santana in order to see if there were any commonalities amongst his home runs surrendered, via Pitch F/X, when compared to other results.  The results showed that, on his home run balls, not only were the pitches right down the middle of the plate but they came in at slower velocities with less movement.  Pythagoras may have never postulated the following but my baseball intuition suggested that:
Down the Middle + Slower Velo + Less Movement = Home Run
It might not be true on every occasion but you would think the above formula rings true more often than not.  A home run–unless at Citizens Bank Park or Coors Field–generally signifies the batter getting “good wood” on the ball; achieving that is intuitively more likely on worse pitches, IE, pitches with less movement, poor location, and slower velocity.
Brian Cartwright of Seamheads commented on the Johan article with regards to curiosity over whether or not the same formula would ring true for other pitchers: Would their home run balls primarily come from less velocity, less movement, and poor location?  Taking the top 20 pitchers in home runs allowed I took to the spreadsheets to find out.
For starters, here’s a look at the overall averages of this group, in velocity and vertical movement (horizontal movement switches signs for lefty/righty) on their gopher balls:

HR Pitch Velocity Vert. Move.
FA 89.87 9.84
SL 82.12 4.09
CU 74.87 -3.62
CH 82.06 5.44

And, when we remove the home run pitches from the aggregate of all pitches thrown by these 20 pitchers, we get these results:

Pitch Velocity Vert. Move.
FA 91.41 9.63
SL 82.29 2.49
CU 75.01 -5.29
CH 82.28 5.44

Looking first at velocity we see that fastballs are around 1.5 mph slower on home runs than all other pitches. Sliders, curveballs, and changeups appear to have increased but since each of them individually comprised very small portions of the overall pitches resulting in home runs, I’d feel more comfortable saying they have sustained velocity. Fastballs are slower on gopher balls, the other three pitches come in at the same speed.
In terms of movement, fastballs have ever so slightly increased movement (0.21 inches) on gopher balls; sliders and curveballs have lost significant movement; and changeups have sustained their movement regardless of whether the result is a home run or the rest.
Put together, their fastballs have been 1.5 mph slower but the movement is essentially the same. Sliders and curveballs are coming in at virtually the same speed on the gopher balls but significantly less movement; IE – same speed but straighter. Changeups, however, have sustained velocity and movement; there has literally been no difference between the changeups hit for home runs and resulting in all other possibilities.
Lastly, for now, here is a location chart of where all of the fastballs have crossed the plate that then sailed over the bleachers for home runs:
fastballshr.JPG
Again, it appears that a high percentage of these fastballs have been right over the middle of the plate. Though these results do not necessarily agree 100% with the Johan results, it seems that the top 20 home run surrenderers are throwing their fastballs slower, with similar movement, right over the heart of the plate.

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