There are three obstacles for Kaka's return to Milan. First of all, there is a tactical issue now that Boateng will play as a quarterback. And the club has already invested in the young El Shaarawy.
For sure, Real Madrid want to transfer the player and could loan him for free. However, his salary is about 10 million euro net per season, too much for Milan.
Finally, his physical condition: Kaka should show that he recovered from the problems who did not allow him to perform in the last two seasons.