Pep Guardiola admits the pressure is on at Barcelona ahead of tonight's Copa del Rey semi-final, first leg at Valencia.

The La Liga and European champions fell further behind rivals Real Madrid domestically over the weekend, with a 0-0 draw against Villarreal allowing Jose Mourinho's side to pull seven points clear at the top of the table.

And it's results away from the Nou Camp which are causing Guardiola the most grief at the current time, something that will again be put to the test against Unai Emery's side at the Mestalla Stadium.

"Living with this constant pressure of having to win and win makes it hard, makes you tense," the Barca boss told the press ahead of tonight's match.

"Sooner or later we'll stop winning. Eventually a better team will come along. That's when we'll have to see if we believe in ourselves. I have to see it to believe it."

When asked on the importance of the competition to Barca this season, Guardiola concluded: "Barcelona need to keep competing, that's what's most important. People can't ask us if we prefer one competition over another."

As for Los Che, they sense an opportunity for an upset, and are hoping to record a positive result that keeps them in the tie ahead of the return leg in Catalonia.

Emery isn't just after a win though, with the Valencia boss challenging his side to record a win by at least two goals, as well as keeping a clean sheet against the FIFA Club World Cup champions.

"Our main priority is obviously to win the match, but that won't be enough," Emery said during his pre-match press conference.

"We have to keep a clean sheet as well and preferably win by more than one goal. Additionally, it's crucial for us to end the match with 11 players.

"We are wary of Barcelona's strength, despite their absences. They miss some important players, but have great alternatives. Barcelona are always a very dangerous team."

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