He said: "We must realise, everyone knows how we play and teams are trying to find new things.

"We have to raise our standards to sustain it and take advantage of the things we have. We try new solutions.

"There are two ways to improve, change – which we will never do – so it's about the building process.

"We've had good performances and bad performances. Watford was not a good performance, Liverpool was a good performance."

Ruben Vinagre is out with a hamstring injury suffered late on the third-round replay defeat at Old Trafford.

Ryan Giles has been recalled from Shrewsbury to help cover Nuno's thin squad.

"It's a massive blow for us. Vinagre is very special for us, he gives us things we need but he is going to be away for a time now," said Nuno.

"He's going to have an MRI to see the extent of the injury but for sure he is going to take some time. He felt it after sprinting 70 metres, he felt something in his hamstring.

"Every time we have a player out it's important. Vinagre gives a lot of things for us to change and operate inside the squad. It's a big blow."

Willy Boly, who became a father this week, remains out with a fractured ankle while Diogo Jota (dead leg) is also sidelined.