Mark Prior's Pitching Mechanics
This clip is one of the most important ones in my library because it shows a number of critical things about Mark Prior's stride that I believe are relevant.
Mark Prior's Stride
This clip shows Mark Prior's linear stride toward home plate, his rigidly upright posture and vertical spine, and his Inverted W arm action.
I would argue that these three things are inter-related, and I say that based on seeing the same three things in the mechanics of other pitchers.
In my opinion, Mark Prior's Inverted W is the result of the linear stride and the rigidly upright posture.
Comparing Nolan Ryan and Mark Prior
The clips below compare the arm actions of Nolan Ryan and Mark Prior, starting when Nolan Ryan's pitching arm is at roughly 0 degrees of external rotation (perpendicular) to his spine.
Nolan Ryan and Mark Prior Frames 15-17
One thing that is obvious is that Mark Prior's pitching arm is internally rotated at the moment that Nolan Ryan's pitching arm is flat and at 0 degrees of external rotation.
Nolan Ryan and Mark Prior Frames 15-18
As a result, Nolan Ryan's pitching arm is well ahead of Mark Prior's from the perspective of sequence.
Nolan Ryan and Mark Prior Frames 15-19
Nolan Ryan's arm is UP while Mark Prior's arm is still FLAT.
Nolan Ryan and Mark Prior Frames 15-21
Postural Differences
Why do Nolan Ryan and Mark Prior exhibit such a significant difference in their arm action and timing?
In my opinion, it's because they move differently.
These postural differences are obvious in the clip below.
Nolan Ryan and Mark Prior
The comparison above is extremely important because it shows that, while Nolan Ryan and Mark Prior got to the same place, they got there very differently and, more importantly, at different rates.
Nolan Ryan and Mark Prior Frames 01-14
Nolan Ryan and Mark Prior's torsos are relatively similar as they start to stride toward the plate.
Nolan Ryan and Mark Prior Frames 14-22
However, they diverge as they go into foot plant, with Mark Prior's torso staying rigid and upright in comparison to Nolan Ryan.
Nolan Ryan and Mark Prior Frames 14-19
In my opinion, Mark Prior's less fluid and athletic movement pattern forced him to compensate by compromising his timing.
That overloaded his arm and worked.
For a while.
Why didn't Tom House teach Mark Prior to throw like Nolan Ryan?
Nolan Ryan and Mark Prior Frames 14-16
In the clip above, notice that, while Nolan Ryan's pitching arm externally rotates and his pitching arm side hand gets above his pitching arm side elbow, the same isn't true for Mark Prior.
Nolan Ryan and Mark Prior Frames 14-17
The clip above shows that the same pattern holds further on in Nolan Ryan and Mark Prior's delivery; where Nolan Ryan's pitching arm is smoothly rotating up and into position, the same isn't true for Mark Prior.
Nolan Ryan and Mark Prior Frames 14-22
In the clip above, notice how, while Nolan Ryan's arm smoothly and gradually gets up, the same isn't true of Mark Prior. Instead, his arm takes much longer to get up; it slowly works its way up, and then pops up at the last second.
Nolan Ryan and Mark Prior Frames 16-18
In fact, Nolan Ryan's arm is up as Mark Prior's arm is just starting to get up.