Kaka now faces four months out of action as he undergoes knee surgery.
"We are very grateful for the effort he made in the summer to go and see several different specialists in Sao Paulo to find an explanation for the problems he was having in his left knee," said Valdano.
The Argentinian claims Kaka's behaviour has been impeccable.
"Kaka's conduct has always been correct and we have never doubted him. He has our full backing and the total support of the club," he said.
"He is an exemplary player and we have never had any complaints about him. Now he must only think about recovering."
Portugal defender Pepe also backed his Madrid team-mate.
"Nobody can doubt Kaka's professionalism," the Brazil-born defender said in an interview with Cuatro.