The Spain goalkeeper has hinted at a possible departure from the Santiago Bernabeu, suggesting he wants to play for a club where he would be considered No.1
The 32-year-old, who is currently understudy to Diego Lopez at the Bernabeu, has spoken of his desire to be first choice again at club level.
Casillas was expected to attend a training camp in Doha - backed by the Iker Casillas Foundation - for around 20 specially selected, young goalkeepers from around the world.
But, due to the possibility of his wife, Sara Carbonero, giving birth to the couple's first child this week, he opted out after medical advice.
Casillas instead spoke to the keepers on a conference call on Friday, dispensing advice from his own experiences and passing on tips for career progression.
At the end of the discussion, he took questions from the group and was asked directly if he was interested in joining Manchester City, the Premier League club managed by his former Madrid coach Manuel Pellegrini.
"I'm not going anywhere [where] I'm going to be No.2," said Casillas, who is under contract with Madrid until 2017.