The Real Madrid star says City will have to strengthen their defence if they qualify for next season's Champions League.
Kaka told the Daily Express: “Like all great clubs who win things, it’s important to build from the back. They could have Adebayor, Torres, Aguero, whoever, in the same team, but unless you have a defence that the rest of the team trusts, you are never going to win a title or European Cup.
“If they make fourth then Buffon, Maicon and players of that quality will suddenly be on their radar and that is when the rest of Europe will sit up and take notice.
“Their next match is so big, but I think they will probably win it. If they do, then it will be the start of a new and very big era for them.”