WB, actually Federer was the big admirer of Rios. Then after that was established after Fed stated so publicly numerous times, Rios responded by saying very complimentary things about Federer's game. Rios was very reserved in giving credits to other players. You will LOL when you read (if you read the book) what he said about Sampras off the record after their French Open match.
Coria, Dolgopolov, Matosevic, Mannarino are all also Rios admirers too.
"He's an extraordinary tennis player on the outside and inside of he's still the normal guy." -Ilija Bozoljac on Federer in the book 'Facing Federer'