Coming off a 1-0 win over Sporting Gijon at the weekend, the 39 year-old coach will be hoping his squad can maintain their position at the top of La Liga table when they welcome the defending league champions.
"The first thing that we should do is believe. The second thing is being able to win," Emery said, according to the official club website.
"We are approaching this game with a winning mentality, but we are also capable of putting it into practise. We can do it, we have belief in ourselves and this is our opportunity to shine," he added.
Valencia will have to contend with an in-form Barcelona, who came back from two draws in a row to defeat Osasuna 8-0 last Saturday.
"Every game is a challenge. Our challenge is two-fold, because of what it means to beat Barcelona and the fact that it would keep us top of the league if Betis drop points."
While taking time to heap praise on Barcelona star Lionel Messi and coach Pep Guardiola, Emery was adamant that weaknesses could be found and exploited.
"Messi is the best player in the world and Barcelona are the best team in the world," he said.
"[Pep] Guardiola has taken this team to excellence, but if we look for defects, then we will find them - as few as they are. We have to play in a way that forces those defects to come to the fore, and that allows our players to win their individual battles on the field.
"We have to be even slicker than before, because we played well the last three times we faced Barcelona and drew two of those games. We are looking to make these necessary improvements - keeping in place the things that we did well last time."
Valencia take on Barcelona at the Mestalla on Wednesday with the game kicking off at 2200 CET.
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