Barcelona centre-back Gerard Pique has admitted that his side are "suffering" but have to "keep fighting" in order to overcome their difficulties.
The Catalan giants have now only won one of their last six matches in all competitions, suffering three defeats in the process, including losses to Bayern Munich and Benfica in the Champions League.
Pique has said that Barcelona could have spent another three hours trying to find the back of the net against Atletico in the capital but would have been unable to make the breakthrough.
"We started well, we went after them, we were brave, [then] they got on top. They scored two goals from very little and, from then on, we could've spent three hours and not scored a goal," Pique told reporters.
"The issue is difficult. It's complicated. We are suffering, I have to be honest. We have to keep fighting, working, rest and disconnect and come back stronger."
Head coach Ronald Koeman will reportedly remain in charge of the team for at least their next three matches against Valencia, Dynamo Kiev and Real Madrid, which all come at Camp Nou after the international break.