The ability to improve velocity depends alot upon the physical maturity of the player and addressing mechanical issues. Many times the player has the velocity but due to poor mechanics and/or physical conditioning top velocity is rarly achieved so he "looks" slow. i.e. my son is in consistantly high 80's, in HS he consistantly threw around 80-83 with occasional throws over 85 or so. Many would say he picked up a few mph while I think he just became more consistant.