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.

Jenry Mejia Pitch F/x

Mejia pitched yesterday for the Suprise Rafters, and didn't do that bad, going 3 innings giving up 4 hits, a walk, a run while striking out 3 in a 2-1 loss to the Peoria Javelinas.
Pitch F/x

Jenry Mejia, 10/26/09
Pitch Type	Avg Speed	Max Speed	Pitch Fx_x	Pitch FX_Z	Count	Strikes / %	Swinging Strikes / %
FF (FourSeam Fastball)	93.99	97.6	-6.18	5.58	37	22 / 59.46%	4 / 10.81%
CH (Changeup)	87.17	88.1	-9.71	3.52	9	7 / 77.78%	3 / 33.33%
CU (Curveball)	77.50	80.2	2.81	-8.18	5	2 / 40.00%	0 / 0.00%
FT (TwoSeam Fastball)	87.75	88.7	-10.93	5.17	2	2 / 100.00%	1 / 50.00%

His fastball has some pretty good sink on it, as Sam Page at Amazin Avenue pointed out in a post a while back. His Curveball also has some insane movement, but he only threw 5 so not much can be read into that, and his changeup has some sink too. He had 14.3% Swinging Strikes.

Met Prospects Pitch F/X

So, if you haven't heard, there are several Mets playing in the Arizona Fall League, on the Surprise Rafters. The Arizona Fall League also has Pitch F/X data, which is what you see on gameday.
It is explained here and here.
The last game that we have Pitch F/x data from (from Brooks Baseball) is October 22, where Josh Stinson went 1 inning, giving up 1 hit, and striking out 1. Stinson is a 21 year old right hander who had a 1.98 ERA in Port St Lucie.
His Pitch F/x data:

Josh Stinson, 10/22/09
Pitch Type	Avg Speed	Avg Pf_x(Horizontal Break)	Avg Pf_z (vertical break_
Fastball (4 seam)	91.07	-6.41	7.94
Changeup	84.75	-9.52	6.75
Slider	82.90	1.99	1.61
Curveball	77.97	6.85	-5.23
2-seam Fastball	89.90	-7.98	5.54

Information gotten from Brooks Baseball, which is an awesome site.
Negative values on horizontal break means the pitch is in to righties, and positive values mean it's in to lefties. 1.99 mean's it's fairly down the middle of the plate.
Stinson threw 13 fastballs, 3 curves, 2 changeups and 1 slider and 2 seam fastball.
So, his fastball breaks inside to righties, his curveball breaks inside and down to lefties, and low and away from righties, which seems to make it a good out pitch.