The former Real goalkeeper, who now plays for Porto, has said that Ronaldo should not be in contention to win this year's award.
Lionel Messi and Virgil van Dijk are also in the running to take home the biggest individual prize in football, and Casillas has made his thoughts clear.
He wrote on Twitter: “[Virgil] van Dijk was chosen as UEFA's best player; [Lionel] Messi was chosen by FIFA. If Cristiano wins the Ballon d'Or, it would seem to me that the guidelines we use in football to determine who wins its biggest individual awards are not logical.”
Liverpool defender Virgil van Dijk is favourite to win the award for the first time after helping the Reds to a Champions League triumph last time out. He has also been an integral part of their unbeaten start to the current Premier League season, after losing out on the league title by a whisker to Manchester City.
Van Dijk fue el mejor jugador para UEFA. Messi fue el mejor para FIFA. Imagina: Cristiano (méritos hace para ello) gana el BALÓN DE ORO, me parecería que las pautas que seguimos en el fútbol para dar premios no tiene mucha lógica, no? Reflexión de viernes. #FelizFinDeSemana— Iker Casillas (@IkerCasillas) November 15, 2019
The UEFA Men's Player of the Year is chosen by 53 top sports journalists, who vote for their top three players, with first, second and third place receiving five points, three points and one point respectively.
FIFA's The Best player is chosen by the captains and coaches of all national teams in FIFA-affiliated federations in five continents, with fans also having a say through an online ballot which accounts for 50 percent of the final result.
These two awards are chosen based on performances throughout an entire season, whereas the Ballon d'Or spans a calendar year, with every match, including friendlies, taken into account, from which 193 sports journalists select their best player of the year.