Zola has likened the youngster to Frank Lampard.
He said: "Frank is more an offensive midfielder where he gets on the ball and scores important goals. Nathaniel can be very offensive as well but we are trying to give him the structure of more of a holding midfielder who organises the play from the back.
"Certainly the talent is there. He needs to work a lot to play at the level Chelsea are at, and as a more defensive midfielder you need to be good with the ball and without the ball; and without the ball I expect him to keep improving."