At the OP, what do you look for when you're trying to gauge a player's skill level?
A couple of years ago, I joined a 9-ball team headed by a D+ player. I out shot him in 9-ball, which is why he asked me to join his team. He wanted me to recruit my B level friend. My B level friend needed to spend more time with his family, and less time playing pool, so my friend suggested another player (Ray) who was currently ranked as D, but had higher potential.
I pointed Ray out to my team captain, and after 15 minutes of watching turns to me and said "Why do we need another D player" "I haven't seen this guy make a hard shot yet". Within a year, Ray's ranking in the local tournaments jumped up to C+, B. My skill didn't improve with that team, and I remained as a D and left after three seasons.
Are you looking solely at shotmaking, what about position play (make the next shot easy), or safeties? See what a player does when he/she gets ball in hand.
I usually focus at a player's skills and technique, leaving more advanced strategic part of the game out of it. IMHO ranking players by strategic performance is an entirely different thing and I wouldn't mix those two up. I mean, a skilled player can make stupid strategic mistakes and a lower player can know all the tricks. But still, I did include the ability to make basic decisions in my system simply because a player's skills are useless if he doesn't know how and when to use them in obvious situations. I'll post the whole thing when I finish the text about it, for now I'll only name the factors:
- accuracy in shotmaking (consistency in easy, medium and difficult shots)
- skills at kicking/banking/combos
- ability to pocket multiple balls on occasions
- knowledge and performance in multiple rail shots
- accuracy and consistency in CB positioning (both for next shot and in safety play)
- positioning of other balls (setting up blockers, driving 8-ball away from opponent's last pocket etc)
- general position and safeties (for example, was anything left out in a safety, or was the 8-ball driven away somewhere where the opponent really can't hit it well)
- knowledge of different shot techniques and consistency in using them (various levels of power, cue elevation, english, masse, jumping, shooting from the air...)
- amount of technical mistakes (miscues, missing easiest shots, applying a wrong type of spin)
- lack of basic skills (usually beginners - unstable bridge hand, constant miscues due to terrible stroke problems...)
- mistakes in decision making (picking shots which are too difficult, applying completely wrong power level, missing out an obvious position or safety when everything else is too risky etc)
- quality of break