The Dutch man who has managed Tottenham and Hamburg, left after the Dutch giants hit a run of poor form and he told the BBC: "With pain in my heart I say goodbye to this wonderful club. "We started something last summer that I would have finished but I have come to realise that the expectations after last season were too high.
"We cannot meet such expectations. The amount of criticism that the club has had to endure daily has led to unrest in the club and among players.
"I take this decision consciously before AC Milan v Ajax is played. The coming weeks are very important and I sincerely hope that something happens in the squad to make it in the short term a winning team."