Striker Fernando Llorente insists Athletic Bilbao can stun a Barcelona side he describes as "unbelievable".

Athletic go into the clash as heavy underdogs but Llorente is hoping the backing of the Basque fans can help them spring a surprise at Valencia's Mestalla stadium.

In an interview with Barca TV, the tall striker said: "In a one-off game anything can happen.

"We have incredible supporters and in the semi-final against Sevilla they lifted us. They carried us forward.

"If we can play like we did against Sevilla in the second game of the semi-final, then we have no limits. Barca are a great side and they will be looking to win, but we will do everything we can."

Llorente claims the spirit within the Athletic squad could also be a factor, adding: "We are a side that are united. The main characteristics of the squad is that we are all friends and there is a marvellous atmosphere.

"That means that when we go out to play we all do so feeling the same way."

The 24-year-old is aware of Barca's strengths, however.

"Barca are unbelievable and are having an incredible season," he said.

"They are the only team in Spain that can win three major honours. But I do not believe they will think our game will be easy."

Athletic have won 23 Copa del Rey crowns but the last one came in 1984 in a game against Barca best remembered for a brawl in which Diego Maradona was particularly prominent.

And Llorente knows just how big a game it is for the club.

He said: "This final is the most important thing that will happen in my life.

"Playing in a final for Athletic is something that people have waited years for in Bilbao and the fact we are going to do so is marvellous.

"I am a player that has come through the ranks at Athletic and to play for not only the first team, but in a cup final is incredible and unthinkable.

"I am so proud and delighted with the way that the team has been playing and I hope that I can enjoy the moment."