Sports Statistics

#1
I am trying to come up with a new way to measure how good any given basketball player is. My name is Tommy, so I'll call it the Tommy Index. My thinking is that the best players are the ones who give their team the best chance of winning the game. The team that scores more points wins the game 100% of the time, so each point that a player scores as an average would count as 1.0 (1x100%) toward the Tommy Index. I'm not sure what the statistics are on how often a team with more rebounds wins the game, but let's say the team that has more rebounds wins the game 70% of the time. If that is the case, a player's rebounds would count as 0.40 (1x40%) toward the Tommy Index. The multiplier is 40% because 70% is 40% of the way from 50% to 100%. Harmful statistics could be subtracted from the Tommy Index. Let's say the team with fewer turnovers wins the game 80% of the time. This means that the team with more turnovers wins 20% of the time. So, turnovers would count as -.60 (1x60%). Here, 60% was the multiplier because 20% is 60% of the way there from 50% to 0%.

Does anyone have thoughts on this. And does anyone know how you'd actually calculate something like this. The key is getting statistics on how often the team with more rebounds, etc. wins the game.