Atletico blew a 2-0 home lead as Barca struck four goals inside the final 20 minutes at the Metropolitano.
Simeone, however, said afterwards: "Congratulations to the opponent. They had that dose of luck, which is also necessary. We didn't take advantage of some counterattacks that we could have taken advantage of. They're a great team, congratulations to them, and we hope to keep working.
"I don't think fatigue showed because we sought new energy with the substitutions. Rodrigo made a huge effort. Julián was feeling unwell, with a fever... and he played as you could see. I can't ask for more than what they're giving."
"I don't think the 2-0 scoreline had any room to be 2-0. They scored and it was 2-1. For any powerful and very good team like Barcelona, this is a boost, a boost of confidence. The opponent enters that space of fear. You can't counterattack; you'll immediately get 2-2. I repeat, congratulate the opponent and move on."
Asked about his team's attitudem Simeone also insisted: "It's clear that there's no need to talk, but rather to see that the team is competing. We've shown that in these last few matches. We need to win.
"We'll fight until the end. There are ten matches left and they have to play each other. If we can and we can afford to have the chance with five matches left, of course we'll give it our all to get there."