Atletico Madrid have missed many opportunities at the same time, being eliminated from the CL competition and losing many points in La Liga matches and so I think the mentality and confidence of Atletico Madrid players has decreased drastically because of that and makes it difficult for them to compete again.
Now Barcelona and Real Madrid will compete for the La Liga title, not to put Atletico Madrid aside but realistically at this time, at the end of the season Atletico Madrid's performance has actually slumped and there is no guarantee that they will recover after a series of bad results like they have now.
Personally, I think Atletico Madrid kicked themselves out of the title race, they were in the title race during their game Vs Barcelona, they needed few minutes to hold on after going 2 goals up but they gave it away and surrendered everything after that loss. I feel for them though but as it stands even Barcelona will not give up that top spot to Real Madrid that's right behind them not to talk of Atletico Madrid.
Atletico Madrid has failed this season as a club because they had all the opportunities to keep their title hope alive but they let the opportunity slipe out because of their inability to defend their goals when they were leading 2:0 against Barcelona I their last match. Atletico Madrid is in a very tight position though the title race is not over but Atletico Madrid will have to overtake Real Madrid before getting closer to Barcelona the current league leaders and that can only happen if both teams drop points.
For Barcelona to remain on top of the league that means they will not drop points so they have to get 3 points from all their remaining matches if they fail to win matches they stand the chance of losing their position and the title race will always be in another teams position.
Looking at the points table in La Liga we can now see that Atletico Madrid are in the third position of the table with 4 points less than Barcelona and Real Madrid. They have dropped back a bit but so far but the points gap with these teams has not been huge, Atletico Madrid still have a good chance. Atlético Madrid just need to perform well and plan ahead in the upcoming matches so that they can get full points in every match. If you do well in every match in front, on the contrary, Barcelona or Atletico Madrid will make mistakes in any match and if they make mistakes, it is because of those mistakes that they will fall behind in terms of points and in that opportunity, Atletico Madrid will be able to go a little higher in the points table. This season their performance is good as a team so if they can't do well this season then they won't get this kind of opportunity in the coming seasons.