The tie is currently level at 1-1 following the first leg last week, but the Argentine has admitted that it will be difficult for his side to overcome the Spanish champions at the Camp Nou.
"For us, nothing has changed. Let's start from scratch. They are better than us and are likely to have more control, more possession and more chances and we will have to be prepared," he told Football Espana.
"The game lasts 90 minutes and we have to know when to hurt them and try to respond in the best way. We arrive with the game open in terms of the result, but on their field and for their characteristics they remain the protagonists.
"But we go into the game with ambition and competitiveness. Tactics? Without breaking the structure we have, we can look for alternatives. There are different ways to win. With our weapons we hope to be able to win the Cup."
Atletico and Barcelona have both taken six points from two games in the league this season.