Johan's changeup

Johan Santana struck out 5 yesterday, and his great change up was particularly impressive. I'm going to look at Johan's tabular data for his changeup.
Velocity Pfx_x Pfx_z Px Pz Break length
80.01 MPH 7.43 6.07 .5 2.2 7.65”

What does that all mean? Here is a useful glossary, done by Mike Fast.
Velocity is obviously the velocity of the pitch, when released. Pfx_x is the horizontal movement of the pitch, in inches. Pfx_z is the vertical movement, in inches. Px is the location, in feet, horizontally. Right is positive, left is negative, and it's from the middle of the plate. Pz is the location in feet, vertically. Break length is the measurement of the greatest distance in inches from the straight path of a hypothetical pitch thrown from the same place.

Here is the location of his changeup
Point (0,-3) would be a right handed batter's feet, approximately.
Here's the average location of his changeup in just the strike zone.
As you can see, it's down and away, which is what makes it so devastating to right handed hitters.