The Ajax coach has said that his side's recent 3-1 Champions League victory over the English champions was due to their own strengths rather than their opponents' weaknesses
An early Samir Nasri strike gave City the lead in the fixture, but goals from Siem de Jong, Niklas Moisander and Christian Eriksen wrapped up an ultimately comfortable win for the Dutch champions.
"We played good football, in certain phases, against a top team," de Amsterdammers coach told Uefa's official website.
"I get tired of people who say it was because of our opponents played badly. Our players were dominating. City had no answer."
The 42-year-old, who won the Champions League in 1995 with Ajax as a player, also spoke about his side's opening defeats against Real Madrid and Borussia Dortmund.
"We did not have a lot of luck against Madrid or Borussia Dortmund," said the retired defender.
"We had most of the possession but failed to take the lead. You cannot afford to miss chances against that kind of team because they will present you with the bill at the end."
The former Netherlands international, who himself came through the Ajax academy, also talked about the continued importance of bringing youth through the ranks at the Dutch champions.
"We invest a lot in the youth academy," said the former Barcelona star.
"More and more, in this time of crisis, we have come to realise that this is the essence of Ajax. It has been going well for many years, but it can always be better.
"Johan Cruyff, in the past two years, has been on top of it.
He added: "He made it very clear that the philosophy Ajax have always had needs to stay intact - for the club and for the image of the club all over the world."