"Games against Chelsea are always important. It doesn't matter what the competition is, whether it is the league, the cup or in Europe," said the Basque midfielder.
"We have to believe that we can get a good result at Stamford Bridge because if we can win there it would give us the belief that we can beat the big four on their own grounds.
"If we want to be challenging for the big prizes then these are the kind of places where we need to go and get good results."
