Tiago says Atletico Madrid must go into their clash at Barcelona without fear.
The former Chelsea midfielder accepts they face the biggest test in football.
He told El Mundo Deportivo: "These are difficult moments because we've not been able to get out of a complicated situation. Right now what we need is to win a game and gain confidence.
"It's the perfect game to gain confidence. There's nothing to lose, they are an opponent who at home and away are very strong and we have a great chance to lift our morale.
"People think that Barca will score five against every team. They did it against Madrid and it seems they are going to do it against everyone, but we don't believe that.
"We are going there with the desire to have a good game and be united, because if we're united we can get something out of the game.
"We have to go out to try to win because, as I said, there's not much to lose. Nobody believes in us, but...we're going to go out and give it everything to try and get an away win."
To achieve that, Tiago said: "First of all, we need to play a perfect game, meaning we have to defend as a team and try to hit them quickly on the counter-attack because we have very fast forwards.
"After that, we need to try and make sure it's not their day, because if they play like they can it is almost impossible to beat them."
Tiago also believes a draw at the Nou Camp could prove a good result, saying: "It would give us a lot of confidence to draw against Barca. It also depends on how you get the draw, but right now it would be worth something to get a draw.
"It's not just for the point itself, but more for what it could mean psychologically for the team."
