To be more precise, if someone is a C player, or someone else is an APA 3 in 8-ball, what does that actually mean? Is the rank simply based on their results (win/loss ratio) in the competitions, or is the ranking system based on certain skills and capabilities of a player? What I actually want to know is if it's possible to "rank" a random player simply by watching him or playing with him for a while, simply from observing the skills and consistency he has shown during all the matches, even if he doesn't play in any league?