Juventus stopper Buffon, however, has leapt to the defence of the 30-year-old, claiming that the former Levante goalkeeper's success at the Bernabeu is an indication of his importance to the team.
"Real Madrid have not lacked anything over the past 10 years, as they have bought the best footballers," Buffon told Marca. "Keylor Navas is a great goalkeeper, despite what some say.
"They have won two Champions Leagues with him and he has often been important on the way to winning them. I don't believe there is a need to sign, as the results have shown that they are winning as it is."
Navas has made 102 appearances for Real Madrid since joining the capital giants from Levante in 2014.