I am definitely in this range on a barbox, BUT not there is a good chance I am not in this range on a 9' which is what the pros play. I can runout like a champ "sometimes" on a barbox with a high gear, but I will pretty much almost always struggle on the big box. Since I struggle on the big box (where I consider the rankings to be more accurate since it is more difficult) I am definitely going to stick with my C ranking of myself. I see players on the big box that are not even short stops shoot better than me on the big box. I rate them anywhere from a B- to B+. I see short stops play on the big box to which I will rate A- to A and then the pros being A+ basically...we will have to agree to disagree on this one my friend.
Matt
The ratings should be done on a 9 footer with proper equipment (no dead rails, no funny pockets, no dinged up balls), as an average over time. If you run 3-4 balls in 9 ball with ball in hand on a 9 footer that would make you a C average. I honestly don't even think about ratings for someone that only plays on small tables or very easy pockets, that is a false sense of how well you can play, like someone playing golf on a short course with holes double the standard all the time, or those guys that are killers among family and friends on their basement tables but are actually C or worse players when going to a pool hall with 4.5" pockets.
A D player is pretty much a beginner, they have no idea how to use angles to play position, not much speed control and can't make simple shots consistently. D player will make 1-2, maybe 3 balls with ball in hand.
C players can pocket balls better and are starting to get playing position, but usually end their turn on a miss or bad shape off a pretty simple shot. Which is why this particular video shows a C player, can pocket balls but not much concept of position or correct shot selection past pocking the ball in front of you. 3-4, maybe 5 balls for a C+ with ball in hand.
B players have position down pretty well, can pocket simple shots almost 100% and can play tougher shots with shape more than 50%, can break and run a rack here and there. Will probably either mess up a tough shot and miss, or get a bit out of line and miss or play a decent safe, where a C player would end the turn a lot often on a simple mistake rather than a deliberate safe. Average 5-6 balls with ball in hand, a B+ can maybe get to 7 balls (basically will beat the 7 ball ghost, which is what I can do. I can't quite get to beating the 8 ball ghost, but I can bet the 7 ball ghost more than half the time).
A players can make tough shots and get position, and most of the time will run out with ball in hand 7-8-9 balls, will not likely end a turn on an unforced error.
That is a solid rating system, and is totally independent of which state or country you play in. A player may be horrible at some games like one pocket, but still be an good B player if they can play position and make balls well, but may not know strategy for specific shots.