It's emerged this week the 17 year-old attacker will join City next year when he turns 18. A fee has already been settled between the two clubs.
Adailton told TMW: "He has everything to do very well. The big names now come here and take the players aged 16-17 because they still have an acceptable cost.
"Real took for example Rodrigo and Vinicius who today seem old but are 21 years old. You need to understand how much a player can grow, because then you find yourself a footballer of triple value.
"Kayky is formidable for his age: he has quality, technique, speed. In a team with a coach like (Pep) Guardiola who is the number one to teach football and develop a player he can exploit everything."