Youth Baseball Curveball Study

My 13 year old son throws a "curveball", and has since he was 11. It is different from the curveball that I learned to throw in that he holds the ball with the same grip as a two-seam fastball, but slightly lifts his index finger off of the ball. His motion arm speed and arm slot are the same as the fastball, but the pitch is slower and breaks down and in. The rotation looks the same and it breaks just like the curveball that I was taught. It took him a couple of years to get command, but it is now his "go to" pitch.

I questioned his coach when my son started working on this pitch; he said that it would not put any more stress on his arm than a fastball would. I did some research and even talked to a former MLB pitcher about it, but couldn't find any info about this particular pitch. He has never complained about his arm hurting, and his strength and velocity continue to increase as he grows.

Anyone ever heard of throwing a curveball this way? Hopefully I haven't made a mistake by allowing him to throw it at his age...

The pitch you describe sounds closer to a cut fastball than a curve. Some may even call it a slurve. Just be careful about him breaking his wrist trying to get a harder break on the pitch I would limit the times he throws it in a game. At 13 his growth plates are still developing. The slider is thrown in a similar way and is tough on the elbow. Cut fastballs are as well because of the overloading of the weight of the ball to one side. If you watch the rotation of the pitch it will spin like a clock this is what produces the 2-8 break for a right hander throwing this pitch, a lefty will see a 10-4 break. His hand will most likely look like he is throwing a knife.

My son is 19 and he has thrown what I call a Little league CB. (11-5) It did not stress his arm and he has never had an injury.
The CB you throw at a higher level has a tighter rotation and breaks later.

Sorry O forgot to mention he was 10.