Carlos Zambrano Injury Explanation

It's been revealed that Carlos Zambrano is suffering from rotator cuff tendinitis but I started noticing a difference in his PFX data as early as June 20th. His delivery changed, his arm slot dropping and by many accounts he started to "sling" the ball in the words of Will Carroll.



The reason why the arm slot will drop down because of rotator cuff problems is an issue of mechanics. The following image is courtesy of athletic scholarship.net.

When the arm raises above the athletes head, the head of the humerus must rotate downwards or the tendons will become pinched between the acromion process and the humeral head. The Rotator Cuff muscles are absolutely key in this process as they have a force couple with the deltoid muscles to keep stability of the shoulder joint and move the arm. The rotator cuff must compress the humeral head into the labrum and rotate the humeral head downward allowing the deltoid to raise the arm above the shoulder. If the rotator cuff is insufficient, the deltoids raise the arm but the humeral head doesn't rotate. The arm cannot raise above the shoulder level without the rotator cuff and the tendons get pinched between the two bones.

Therefore, instead of coming from "over the top" the pitcher must drop down to 3/4 or approaching sidearm. Another adjustment is what Zambrano did by dropping ones elbow and shot-putting the ball up to the plate.

Tendinitis can caused by several things including laxity (looseness) of the shoulder or elbow, muscle imbalances, labrum tears, or overuse. Without seeing him everyday I can't give you an exact reason but normally in power pitchers it's a combination of muscle imbalances and very minor looseness.

Based on how long he appeared to have an altered throwing motion, it will likely take just as long to get him back to 100%. I expect that he's going to be around a week or two away from being able to pitch in an MLB game again. He's probably going to be on a strict pitch limit when he comes back which is the smart things to do. Hopefully this will help set up a Cubs-Red Sox World Series.