After starting the season in great form, Valencia are without a win in four La Liga games and have dropped down to fifth place in the table.
However, Nuno believes the spirit is still there to enjoy a successful season, starting with Saturday's clash at the Mestalla.
"What we have is a great desire to win, it is critical to our objective," he said.
"We come into this game off a bad result, but there is no anxiety. There is an eagerness to get the game underway, battle and come away with the win.
"This year we have had some good times at Mestalla, some euphoric moments and some late disappointment. What we have always had is a team that fights, that never gives up and who are always looking to score and win.
"That gives me confidence; the most important thing is the attitude we have at Mestalla in front of our fans."
Valencia beat Rayo 2-1 in the first leg of their Copa del Rey meeting, with that tie to be concluded on Tuesday.
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