There is another opinion - or again speculation - that Kaká has his sporting difficulties in his head. They suspect its psychosemantic - again speculate - & that the player does not feel up to it on the field in order to give his 100%, that his pains in the knee are mind induced.
Said all this , we can only guide ourselves with what we are allowed to see, that is, his last on field match performances. What I saw was a slightly overweight player, with loss of muscle in the leg area & very, very slow in movement. It was not the Kaka we all have seen in AC Milan & that fascinated the World.
I hope that the Brazilian gets back soon, simply for the good of Football. The rumour is however that the shadow of surgery is looming, I hope that can be avoided.