Pitching Mechanics Analysis
Kerry Wood

2/25/2008

Kerry Wood, like Mark Prior, is a pitcher who showed tremendous promise when he first came up but then experienced a series of injuries. I think Kerry Wood's problems are due to both his mechanics (and a timing problem) as well as his reliance on his slider.

Arm Action And Timing

A pitcher's arm action and timing are the primary determinants of the long-term health of their arm, so it's always the first thing I look at. As the clip below demonstrates, Kerry Wood's arm action demonstrates some problems.

Kerry Wood

The issue is that, like Chris Carpenter, BJ Ryan, and Scott Williamson, Kerry Wood has some Inverted L in his arm action. This hurts his timing and is the root cause of his shoulder problems. It probably also has something to do with his elbow problems.

Kerry Wood's Inverted L

You can see Kerry Wood's Inverted L at Frame 73 of the clip above.

Kerry Wood's Inverted L

Kerry Wood's Inverted L is easier to see in the still photo above, which is from basically the same moment in time. The thing to notice is how his Pitching Arm Side (aka PAS) elbow is at the level of his shoulders and his PAS forearm is hanging down beneath it. This will increase the distance over which, and the force with which, Kerry Wood's PAS upper arm will externally rotate, which will put significant stress on both his elbow and ultimately his shoulder. One thing I should note is that Kerry Wood's Inverted L isn't as bad as BJ Ryan's.

BJ Ryan's Inverted L

Overall Pitching Mechanics

Now that I've given you an overview of Kerry Wood's arm action, let me get into the details of his overall pitching mechanics. 

Kerry Wood

I'll do this using some individual frames from the clip above.

Kerry Wood - Frame 63

In Frame 63, you can see that Kerry Wood breaks his hands at his letters.

Kerry Wood - Frame 70

Up to this point Kerry Wood's mechanics aren't terrible. He breaks his hands mostly in line with Home Plate and Second Base, which means that he does not excessively reverse-rotate his shoulders. One thing that Kerry Wood does that is slightly inefficient is that he seems to open up his hips prematurely. Notice how in Frame 70 his toe is already starting to point toward Home Plate. You can see the same thing in Frame 63.

Kerry Wood - Frame 71

Frame 71 is where Kerry Wood's arm action starts to go off the rails. In Frame 71, Kerry Wood starts to pick up his elbow.

Kerry Wood - Frame 72

By Frame 72, Kerry Wood is well on his way to the classic Inverted L position. Notice how his Pitching Arm Side (PAS) elbow is at the level of his shoulders and his PAS forearm is hanging down beneath it.

Kerry Wood - Frame 73

In Frame 73, Kerry Wood's timing problem becomes obvious. He is starting to pull back with his Glove Side (GS) elbow and his shoulders are starting to rotate, but his PAS is still mostly pointed down toward the ground.

Kerry Wood - Frame 74

In Frame 74, Kerry Wood has continued to pull back with his GS elbow and his shoulders are continuing to rotate, but his PAS forearm isn't yet horizontal (much less vertical).

BJ Ryan's Inverted L

Kerry Wood's Inverted L

One thing to note is that Kerry Wood's Inverted L isn't as bad as BJ Ryan's, which I think might be somewhat significant. While BJ Ryan's PAS forearm hangs down vertically and his elbow is bent 90 degrees, Kerry Wood's PAS forearm is angled back toward Second Base. I think that might help to explain why Kerry Wood has been able to come back from his shoulder problems without needing major surgery.

Kerry Wood - Frame 75

Kerry Wood - Frame 76

Kerry Wood - Frame 77

In Frame 77, Kerry Wood's PAS forearm is finally vertical and in the high-cocked position. However, notice how much his shoulders have opened up prior to this point. I'd say his shoulders have rotated 30 or so degrees. This will increase the force with which his PAS upper arm will externally rotate and will increase the load on his elbow and shoulder.

Kerry Wood - Frame 78

In Frame 78, Kerry Wood's PAS upper arm is starting to externally rotate and his PAS forearm is bouncing or laying back toward Second Base.

Kerry Wood

Because of his timing problem, Kerry Wood's PAS upper arm externally rotates especially much and especially hard. This is one reason for his shoulder problems (and his elbow problems as well).