He said: "It was of course really difficult, it was a tough decision because I spent two and a half wonderful years here.
“Not just professionally, I'm talking personally as well. My family enjoyed living in New York and being part of what New York City FC tried to build so it is a difficult decision.
“Since I have been in this football club it has been a real pleasure to work with the players I had.
“They made my job easy because they are hard workers and buy into the project and philosophy. The success I had here opened some different doors for myself."