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The REAL Reasons MLB Pitchers are Getting Hurt

There are all sorts of theories being pushed blaming the pitch clock and WBC for pitcher injuries this year.

Here is the truth- pitchers have been getting injured more and more for many years. as shown in my article in February every team is using more pitchers in a year than ever before.

This is BEFORE the WBC and BEFORE the pitch clock. We don't have the data to say either of those two factors are doing anything yet.

I think it has EVERYTHIBG to do with TWO factors. Here is MY THEORY. The issues are REALLY:

  1. Velocity

  2. Pitch Usage- the number of sliders and curves being thrown in the modern MLB

I am not going to go into the biomedical physics of the human arm and the effects pitching has on it. I just want you to understand a few of things.

  • Increased pitch velocities require increased acceleration of the arm.

  • Increased acceleration requires more force.

  • Force cause stress on the joints.

  • Repeated stress causes fatigue.

  • The weakest joint has fatigue failure first.


  • Throwing a straight fastball allows the strongest joints, ligaments, and muscles to execute the pitch.

  • Inducing "break" (sliders and curves) puts stress on and fatigues the weaker joints and ligaments in the arm.

The injury a pitcher has when he is 30 years old started when he first started when he was a kid. It was accelerated when the teenager decided to start throwing sliders and curves. There IS a reason why MANY trainers say no teenager should be throwing anything but a fastball until there arm is FULLY developed.

Here are two revolutionary statements

  • The Human Body has Limits

  • The Game of Baseball has gone beyond those limits


The graphs on the left show the increase in average velocity for each pitch since 2008 (the statcast era for this data from

In 15 seasons the average pitch has increase 2.2 mph. For those of you who want the details here are the numbers.

The largest increases in velocity have come on the curveball (76.5 to 79.5 mph) and the change-up (82.3 to 85,3 mph). Oh no we are throwing curveballs faster than we EVER had. Go back to the beginning to refresh why that is bad.

Pitch Usage In the table above I also showed the usage percent for each pitch. Here is what that looks like graphically.

The largest increase in usage has come on the slider (13.9% to 20.8%). That is a MASSIVE increase in probably THE most ligament harming pitch known to mankind. We have a slider usage problem folks.


Throwing a baseball two mph faster may not seem like much. However, sliders and change-up are thrown at speeds that pitchers 40-50 years ago threw their fastballs. All of this illustrates the max effort and stress that pitchers are now throwing. THIS is a big part of why the stamina is down and injuries are up because the max effort is up. The stresses of throwing with this effort leads to the number of pitchers the modern game has AND the injuries the current game has.

I am going to boldly say that the WBC and the Pitch Clock DOES NOT REALLY MATTER. Any effort to change those things will lead to minimal results. What matters if the drive for velocity and for using breaking pitches.

Here is the problem. How do you get pitchers to slow down and throw less breaking pitches? The only way I know is to make control more important. Make the strike zone smaller. Make it where a player that has gotten to 10 pitches at the plate appearance and who has gotten three balls is awarded a walk. Incentivize throwing strikes.

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