Michael Joyce rates Rios talent above Agassi and Sampras
"I played with Agassi and Sampras two or three times each. But I always tell people that Rios was the best tennis player that I ever played. If he had the same mental as Agassi, I mean...he was tougher than Agassi to play. The things he could do on a tennis court were amazing." --Michael Joyce (From Rios book "Marcelo Rios: The Man We Barely Knew")
Strong praises by Michael Joyce but you have to respect his point of view, having played each of the players numerous times. Rios was a wonder of a talented player, so unique and distinct, yet confusingly mysterious.
Facing Federer book was called "pretty addictive" by Steve Tignor :)