Before we offer our opinion, look at what world renowned sports orthopedic Dr. James Andrews (J.A.) has to say in this Q and A.
1) Just as Dr. Andrews stated, it's a hard pitch to throw. It takes neuromuscular control to throw it properly, and many youth players do not have the neuromuscular maturity to execute throwing a curveball with proper mechanics. Too often we see kids try to create spin and break by lowering and leading with their elbows and by getting their wrists under the ball to try and create spin. We also see highly inconsistent arm speed (slowing down the arm during the throw).
2) Kids and parents become infatuated with the pitch and as a result it's thrown much too often. This goes for kids that can even throw it correctly. If your kid cannot consistently throw strikes with his heater, and also have the ability to command his fastball up, down, in and out, then you are doing a big disservice to your kid by having him throw a curveball.
Three of the most important keys to pitching: •Be able to consistently throw strikes with your fastball •Get outs by commanding your fastball •Stay aggressive with your fastball
If your kid cannot perform these three keys every time he takes the mound absolutely do not think about introducing a curveball to him.
3) Most kids and parents don't know when and how to use the pitch. It's not an automatic curveball situation when you have a hitter 0-2 or 1-2. We see kids throwing it behind in the count (1-0, 2-0, 2-1, 3-2) all of the time, which is a big no-no.
Your kid should have two pitches that he can utilize well before ever learning to throw a curveball - a fastball and a change up. Quite frankly, a youngster who is good enough to make his high school team should be challenged to successfully navigate high school hitting lineups from his freshman year to his senior year with only a fastball and change up.
It would be wise to teach your kid a more simple pitch like a "cutter" (cut fastball) rather than a curveball. A cutter is thrown just like a fastball with a slightly different grip, and is a devastating pitch to a hitter if thrown correctly. Ever hear the name Mariano Rivera?
If your kid can consistently throw strikes with his fastball, utilize his change up or cutter effectively, has a solid set of mechanics and maturity, and is around 15 years old, then you can introduce a curveball. The curveball should be treated like a reward for youth players. As examples: can be thrown twice per inning only when ahead in the count, or get through the opposing lineup one time without a curveball and then it can be thrown two or three times per inning the following innings.
Lastly, have someone, or a few people who have played at a high level themselves take a look at your kid's mechanics and how he throws his curveball. There's no one better prepared to teach the fundamentals and intricacies of baseball than those who have played at the highest level.