Diego Simeone rues Atletico's lack of precision in stalemate with Espanyol
Atletico had 25 shots on goal but Espanyol's defence were up to the task with several blocks and clearances while the visiting side's goalkeeper Joan Garcia made seven saves to go home with a valuable point.
Simeone said his side were undone by a "lack of precision" in front of goal.
"It worries me, as always, but I can't stop appreciating the good game the team played. When you have five clear goalscoring opportunities like the ones we had?" Simeone told Movistar.
"Well, they didn't go in, but the opportunities we created were the result of our play, not by chance. We expected to win, but they defended well and we were not convincing. If you don't score, it's very difficult.
"The team played very well, they made a very strong start to the first half. Then we dropped off a bit, that's why we made the changes. In the second half, we didn't have so many chances to score, but we played well."
Simeone made three changes at half-time to freshen things up, with Antoine Griezmann, Marcos Llorente and Pablo Barrios coming on, although eyebrows were raised when Norwegian striker Alexander Sorloth was replaced by defender Reinildo.
"We never changed the system, we continued with a 5-3-2 (formation) to balance the team, which was starting to split," Simeone said of his half-time substitutions.
"The opponent could also hurt us and we balanced the middle with Llorente and Barrios."
While it was two points dropped for Atletico, it was a first point of the season for Espanyol and their manager Manolo Gonzalez.
"I think that football has been unfair to us up until now. The point is important because it strengthens you on a pitch like this," Gonzalez said.
"It strengthens you mentally. If you are capable of competing here, you can do it on any pitch.
"We didn't defend well in the first half and it could have cost us the game. We managed to hold on and that gives us a lot of strength. It helps us reinforce the work we're doing."