The Madrid outfit have lost three games on the bounce and their coach has conceded they are beginning to suffer after a long season
The capital club are level on points at the top of La Liga with Real Madrid and Barcelona and have made sound progress in the Champions League, but have suffered three defeats in succession, including two losses in the Copa del Rey semi-final to Carlo Ancelotti's side.
Simeone has admitted that his team are fatigued after an exhausting campaign thus far, telling La Gazzetta dello Sport: "The team might be tired, but their continuity has been one of the key factors for their sense.
"If others had played, no-one could be sure that we would be in this position. But two of the losses were in the Copa del Rey against one of the best teams in the world, Real Madrid.
"Eight days ago, were leading La Liga. Sooner or later, all teams go through some difficult times, let's see how we do after 38 games. Madrid and Barcelona have quality that makes a difference in the long term."
Atleti face AC Milan in the last 16 of the Champions League and Simeone is refusing to underestimate the Rossoneri, despite their poor Serie A form.
"Milan are always much stronger in the Champions League than in Serie A. They always do well in Europe traditionally.
"It'll be tough. They have many champions and we have to be very humble, knowing that they'll give their all.
"Massimiliano Allegri's Milan were suffering this year. Now Clarence Seedorf is there and he has to form a team."