Atletico Madrid must immediately improve their standings if they do not want to lose the opportunity to stay on the path of champions. But this week will be a tough week for them, because the team they will face is their rival as well as the team that won 100%, Real Madrid. If they lost this match, it would be more difficult for them to move forward.
Atletico Madrid has 10 points which is 5 points less than Real Madrid. They are not too far from top 4 and only 2 points less than Ossasuna which stands at the fourth position. They must have at least 1 point from this match to prevent Real Madrid expanding the gap with them. I believe Athletico Madrid wants to join La Liga championship competition. They don't satisfy to join only top 4 of La Liga.
Even though they will try to get up, when the opponent in front of their eyes is Real Madrid, it will be very unfortunate. Atlético Madrid's mentality last season was quite good but now they have lost confidence in the midst of player instability and the coach's strategy is not accurate in front of the opponent. Real Madrid will test them on the pitch. If until now Atletico Madrid still does not try to get out of the pressure it could end badly for Diego Simeone's reputation.
Things are not too bad for them at least now. One win can help them to move upwards on the table. The season is only at beginning phase and they have many matches to improve their standing.
I disagree if you say mentality of Athetico Madrid is weak. They are too strong mentally from their coach to players.