Bayern began their Champions League title defence with a thumping result on Wednesday night.
Simeone reasoned later: "I'll take the attitude of my team away from this match as a plus. We kept looking for a goal right until the end. We even had a few chances and with better finishing we'd have scored a couple. That was a big difference – Bayern's finishing.
"I'm really not sure whether we committed a bundle of errors, or the key was their virtue of how well they exploited possession if they won it back and unleashed counterattacks on us."
Atletico midfielder Hector Herrera also insisted: "We played very well, we went toe-to-toe with the European champions, the best team in the world. Perhaps it cost us in the scoreline but we made our opportunities."