Zola told the Watford Observer: "We are still looking for players.
"We will see if there is anything and we will need to work on that. It is the same as Tom Carroll, we will try and attract the players with what we can offer.
"We can't offer what other clubs can in terms of money, but I think we can attract players. Nathaniel knows what we are and Chelsea know the type of work we do.
"We can still give Nathaniel something to help him develop. So I am relying on this and we'll see what we can do.
"We are not struggling, so we will see what we can do. If we can't improve the team then we will stay the way we are."