City have reportedly had an offer for Ake accepted by Bournemouth.
BBC Sport states Bournemouth have accepted a £40m offer from City for the Holland international, with a further £1m due in bonuses. Ake joined the Cherries three years ago from Chelsea and has made 121 appearances for the club.
With Bournemouth suffering relegation, Ake is seeking to remain in the Premier League and the chance to play for Pep Guardiola's City is attractive.
But Kieft isn't convinced about Ake and whether he is the right fit for City.
And referring to City's defensive problems this season, Kieft told De Telegraaf via Voetbalzone: "Aké will discover that it is a job to play there and that he will also have the biggest problems.
"Aké can play a nice ball and has eight years of experience in England. They will have bought him on his defensive qualities, although he is strongest when he plays around the sixteen metre box and that happens less often at City. I sometimes find him a bit wild.
"It will be a concern (for Holland) if he is considered a reinforcement for squad depth. He draws and will earn a huge salary for five years and he will end up in a great squad."
Kieft also said: “Manchester City can buy a player who they don't even know for 40 or 45 million euros.
"They just keep on going and you see the power of capital."
- updated August 3