For what it is worth- I watch a lot of pro ball and I see guys with horrible CU's- not any different than high school. We talk about a big league change-up and stuff but in reality the only real difference is velocity. I see professional pitchers who slow the arm motion down, change arm slot, etc. when throwing their cu. On the flip side I have seen kids in hs with scarier than @#%$ change-ups. There are fewer kids in hs that throw convincing cu's, but you see the same thing in professional ball too. Not very many professional p[itchers who use a cu as their out pitch- just not convincing enough.