The 29-year-old Brazilian – signed on loan from Real Sociedad last month with the option to buy for £22million in the summer – has made five appearances so far without scoring.
But Nuno is ‘optimistic’ that the centre forward will break his duck soon, as long as he carries on working hard.
“He has to keep improving and committing himself to what he is doing,” said Nuno.
“He is going to play, against a tough opponent and very good defenders.
“There are some things he has to challenge himself on and overcome.
“At the same time, the team is here to support him and to help him.
“What he is doing for the team is very good – and we need it. He is giving back, so things will go better.
“The only way is to commit everybody, so I am optimistic regarding Willian and his performance in the team.”
Jose was brought in to bolster the attack during the absence of Raul Jimenez, who Nuno says is now joining in with group warm-ups at Compton as he continues his recovery from a fractured skull.
“He is training, most of the sessions are individually,” said Nuno.
“He’s been able to integrate in some parts of the beginning of training sessions – some things like that.
“We have to be careful and follow the protocols, while keeping positive because he’s doing really well.
“We are delighted and happy, knowing it will take time, but he’s in the right direction.”
On if Jimenez could be back in a matter of weeks, Nuno added: “I cannot say. We have to follow the guidance of the doctors and be patient – avoid any mistakes.”