Real Madrid managed to land Casemiro on the cheap last season.
The former Sao Paulo midfielder signed permanently this summer after spending six months on-loan at Real last season.
At the time, the Brazilian club said "no" thinking that the player could go for even higher, but the reality is that in the end Real only coughed up 6m to sign the youngster.
"We have turned down offers of more than 10m for him. But that's football. One rejects an offer of 10m hoping that he will sell for 20m, but then comes a slump and it changes everything," said a source close to the Brazilian club.