Real Madrid icon Iker Casillas has questioned Juventus star Cristiano Ronaldo's favouritism for the Ballon d'Or.

Casillas who now plies his trade for Porto, believes that former teammate Cristiano Ronaldo should not be in contention to win this year's award.

"[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," Casillas tweeted.

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, three and one point respectively.

FIFA's 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, which is then chosen by 193 sports journalists.