Occasionally, I write comments on a blog that talks mainly about basketball and sports in general. With some of the frequent readers the same old debate arises again and again: who are the greatest basketball players of all time? Of course, every time this question is raised, it is followed by endless discussions.
In general, this question does not excite me for the following reasons:
- It is virtually impossible to compare players who played at different times 
- The judgment would be influenced inevitably by subjective factors.
Even though I’m not passionate about this kind of problem, a new “approach” came to my mind several weeks ago. Assuming that it is not possible to measure the overall value of a player , I wondered if it is somehow feasible to find an overall relative judgment rule.  In other words, I tried to find a general approach that allows establishing if player A is better than player B, even if they performed in different periods. To do that, I had to think about something that is loosely related to the era in which the considered players performed. At the end of the day, I thought about a rule that is expressed in the form of a question that you have to ask yourself. First, you have to pretend that:
- You are a basketball player
- You want to fully develop your potential by improving all the aspects of your game
- You can choose one and only one player to pass on his knowledge about everything concerning basketball (fundamentals, mental and physical preparation, teamwork, leadership, etc.)
- All the players are equally good at passing on their knowledge.
Under these conditions, to establish which one is better, just answer this question: would I choose player A or player B as “the teacher”?
Of course, this method can be applied repeatedly to couples (or groups) of players to determine the greatest ever. Just put them in a bracket and eliminate them progressively as shown in the following picture.
You will end up with one with one player, your GOAT  according to this definition, no matter how you sorted them initially .
 If we treated this issue with a scientific approach, we would say that the boundary conditions—for example, the rules and the level of the opponents—are so different that the athletes are just not comparable.
 Apart from specific athletic skills such as vertical elevation or 100m sprint time.
 Actually, the NBA is trying to define a lot of sophisticated indexes, based on real statistics, that are born to compare players. In my opinion, these indexes are suited to express specific skills such as efficiency and productivity but none of them can summarize the overall value of a player.
 Greatest of all time.