Simeone’s men went into the match at El Sadar needing a win to remain level with Real Madrid at the top of La Liga, but they came unstuck against a determined Osasuna side.
Alvaro Cejudo netted their first in the sixth minute, before Emiliano Armenteros doubled the lead 15 minutes later with an excellent attempt from 25 yards out.
Roberto Torres added a third just before half-time and Atletico rarely looked like eating into the deficit as they appeared bereft of ideas in attack and Simeone paid credit to the Pamplona club afterwards.
He said: "When the opponent is better I congratulate them. Osasuna played well today.
"The second half was better for us but the goal to put us back in the match didn´t arrive.
"Osasuna played well and surprised us in the first two goals, completing the first half very well.”
Atleti left-back Filipe Luis echoed his coach, maintaining that the better team won before reminding his team-mates that they face a tough task in their next match as Real Madrid visit Vicente Calderon.
"They (Osasuna) have been better," Filipe admitted. "They have taken their chances. We have to congratulate them.
"We must think to the next match. At home we are very strong and we are going to try to beat Real Madrid."
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