Speaking to the media, Emery said: "My challenge with him is a huge challenge. His challenge with us is exciting.
"I don't want to know the reason he is leaving from Manchester, but I am very happy keeping him here and I am very happy to try to exploit and help him recover his performances, individually and collectively.
"The conversation I had with him was a very normal conversation with a player and coach, speaking about football. I only want the best football from him. I think he has huge potential to exploit."