Michael Joyce rates Rios talent above Agassi and Sampras
This is easy to do. "Talent" is an abstraction, an unknown.
One can only have impressions or opinions of it, and one cannot be proven wrong, because when talking about "talent" one is not talking about objective, measurable achievements.
I prefer achievements.
The fundamental cause of the trouble is that in the modern world the stupid are cocksure, while the intelligent are full of doubt.