Both players are up for the most prestigious prize in football, along with the favourites Cristiano Ronaldo and Lionel Messi.
There have been many calls for the award to go to a member of the Spain side, who have been dominant for a number of years. Xavi has backed Casillas, who is the current captain of La Roja, insisting that should be in the running for the award.
"He is the type of player who unites a team, though." said the 32-year-old.
"I don't think there's any need to discuss his footballing qualities,
"Evidently Iker should be among the candidates to win the Ballon d'Or."
A list of the 23 candidates for the Ballon d'Or will be revealed on October 29.