Kaka denies hiding injury from Real Madrid
The midfielder has been criticised for playing with the injury at the World Cup.
"I had some problems but I didn't realise it was serious," he told As.
"I notified Madrid at all times. It was troubling me at times, but I thought it was something normal and I knew I would have a medical examination when I arrived.
"I have to say that I'm not the bad guy in the film - I need people to believe in me."
The playmaker says he will work hard to return to form and fitness, and hopes to help Madrid win titles this season.
"I will do everything in my power to get better as soon as I can and to win titles with this new Madrid," he said.