Its no secret that the NBA is a stats driven league, the most popular of which are one-number player-evaluation metrics. While most agree that using only one number to evaluate an NBA player is foolhardy, that doesn't stop them (or me) from trying. Its a challenge, its intriguing, and most of all, its fun.

Therefore, I decided to make a quick post detailing "what" makes a one-number metric useful, and how to spot potential problems in popular metrics.

A good metric can't be a black-box. For instance, one may disagree with what Wins Produced (WP) says, but its very clear

Conversely, one may agree with Plus/Minus metrics, but its unclear

Stability indicates that the metric is measuring

That's all I can think of off the top of my head. Apologies for the word-heavy post, with not a colorful table in sight.

Therefore, I decided to make a quick post detailing "what" makes a one-number metric useful, and how to spot potential problems in popular metrics.

**Accuracy**

__Explaining the past__- Take the "metric-score" for each player in 2012, multiply it by their minutes played, and add them up by team. If the metric is accurate, the teams with the highest scores will be the teams who win the most games.__Predicting the future__- The same as above, except you multiply the 2012 scores by the minutes played in 2013, and sum according to 2013 rosters. A high correlation between the team scores and winning percentages indicate metric accuracy.__A metric that "explains" without "predicting", or visa-versa, can't be considered extremely accurate.__***WARNING*****Transparency**A good metric can't be a black-box. For instance, one may disagree with what Wins Produced (WP) says, but its very clear

**how**to calculate Wins Produced, and**what**a player must do for a high WP score.Conversely, one may agree with Plus/Minus metrics, but its unclear

**what**specifically a player can do to increase his Plus/Minus, which could be detrimental to a coach making in-game adjustments.**Stability**

NBA players perform at somewhat consistent levels from year to year. If a player's metric-score fluctuates wildly from one season to the next, then there could be a problem. If many/most players under a certain metric have their scores fluctuate wildly, then there's definitely a problem.Stability indicates that the metric is measuring

**something,**as opposed to picking up random noise**.****Versatility**

A good NBA metric can be broken up into smaller, but useful parts. I can use a component of XRAPM**(****D-XRAPM****),**to evaluate a player solely on defense. I can use the scoring component of Wins Produced**(Net Points)**to evaluate scoring prowess. Basically, a good one-number-metric is more then that one number. It can illuminate multiple facets of the game.That's all I can think of off the top of my head. Apologies for the word-heavy post, with not a colorful table in sight.