Los Che were hammered in Switzerland but the midfielder says they can turn the tie around at Mestalla, claiming they had been affected by playing at an empty stadium
The former Getafe midfielder conceded his side had performed poorly but said they found it difficult to cope with playing in front of an empty stadium.
Parejo also believed the three-goal winning margin flattered the hosts and spoke of his belief that Valencia can still turn the tie on its head next week.
“We immediately have to think about next Thursday,” said the 24-year-old. "We will go with everything we have got and the fans will have an important role to play too.
“It is complicated, but when we are at home with our fans, we believe we can turn it all around. The home supporters will see a Valencia side who wants to be in the semi-finals of the Europa League.
“The team were not comfortable in the first half. We noticed the environment with no spectators – that is not an excuse, but it was part of the problem.
“Being 2-0 down at the break clearly shows we have not been successful, but I do not think they had the opportunities to warrant the advantage they have over us.
"The coach has given us guidelines at the break and we did respond but it was too late.”
Paco Alcacer was also attempting to stay positive after what had been a torrid night for Los Che.
“We must forget this game now – we have not performed in a way that is expected of Valencia,” he said. “In the second half we had chances to get into the tie but the end result is what it is.
“We must think positively. At the in Mestalla we have to give everything. We need try to like crazy men to get the first goal on the night. If we can do that, we will quickly have opportunities.”