Atletico Madrid boss Diego Simeone believes victory over Barcelona will only be possible if his side remain disciplined and patient throughout the tie.
The Rojiblancos face the Liga champions at the Vicente Calderon on Wednesday for the first part of the two-legged affair before travelling to Camp Nou on August 28.
Although Simeone admits his team go into the clash as underdogs, the Argentine has stressed his charges are capable of upsetting the odds provided they play to their own strengths.
He told reporters: "When you go into a game you need to know your strengths and your opponents' strengths as well.
"They have many strengths and we have some too and it's vital we know how to use them.
"We need to be patient, disciplined and tight at the back so we can take advantage of our opportunities.
"Barcelona are without a doubt the better team. They have Messi, the best player, and in Neymar they've bought a player who could become the best player in the world.
"They have a lot of important players and it's no surprise they are favorites, but we will fight them with all our might."
The 43-year-old, who led the capital club to a third-placed finish last season, went on to admit he is hopeful about breaking Real Madrid and Barcelona's stronghold as the dominant teams in Spain, having claimed earlier this week that La Liga is made "boring" by the dominance of the Clasico clubs.
He added: “It's very difficult for either of them to have a bad season. We hope their domination won't last forever, because fans want to see their team win."