Back in Europe's elite club competition after a two-year absence, Valencia are second in the section on three points from two games, three behind leaders Zenit St Petersburg, who beat them 3-2 at the Mestalla two weeks ago.
Nuno and the players have been subjected to some sustained whistling during a series of below-par performances in La Liga and they are eighth after managing only two wins in six outings in Spain's top flight this term.
They face a difficult trip to play Athletic Bilbao on Sunday and Nuno said that while the team should be proud of their achievement in Lyon there was plenty of room for improvement.
"We are not euphoric and we have to focus now on our next match in the (domestic) league," he told a news conference.
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"But we can be happy and proud of the work we are doing," added the Portuguese, whose credentials have been questioned following the team's stuttering start.
"The main thing is that we all believe we are doing things well. We have to show belief and work a great deal so that we can achieve success in the future."
After the match in Bilbao, Valencia have a couple of weeks to regroup during the international break before they host Malaga on Oct. 17.
The following week they host Ghent in the Champions League before a crunch La Liga clash at Atletico Madrid on Oct. 25.
Valencia were runners-up in Europe's elite club competition in 2000 and 2001 but financial problems over the following decade forced them to sell many of their best players and they have struggled to compete for titles.
However, last year's takeover of the club by Singapore billionaire Peter Lim has raised hopes they can return to the top in both Spain and Europe.
(Reporting by Iain Rogers, editing by Sudipto Ganguly)
