Jonathan David opened the scoring in the 24th minute, continuing his fine start since joining the club, before Kang-in Lee doubled the lead early in the second half. Robin Le Normand made it three from a corner won by new signing Cristian "Cuti" Romero, and Álex Baena completed the scoreline late on with an assist from Johnny Cardoso.
The result was overshadowed for Osasuna by a contentious refereeing call midway through the game, when Iker Arguibide's effort was ruled out after Lucas Torró was penalised for a foul on Le Normand in the buildup. Head coach Luis Miguel Ramis said the decision summed up a frustrating run.
"It's a duel up top between two players who clash heads and the ball comes away loose," Ramis said. "Beyond the fact the game could have finished with a win for Atlético, it's another decision that condemns us and hurts us.
"I don't see a foul, although that's no excuse for the defeat. We're not having luck with these kinds of situations.
"The penalty not given the other day is a scandalous decision, and for me, so is this one."
Ramis added that officials had taken only seconds to rule the goal out, and questioned the standard of proof required. "As always, in three, four or five seconds they review it. I've jumped for headers thousands of times in twelve years as a professional, and you can split an eyebrow or someone gets a touch on the ball first, but these are 50-50 duels. Le Normand didn't even complain."
Still, the Osasuna coach did not want to blame officials alone for a heavy defeat.
"The result is emphatic enough that we can't hide behind this. We have to correct a lot of things, especially the second goal, which is the one that really hurt us," he said, also pointing to rotations made after losing 2-0 at home and 5-0 in Vitoria in recent weeks.
Simeone, by contrast, was delighted with a near-complete performance.
"It was a well-rounded game. We always expect the best, and in the first half we already expected to go in more than a goal up — they worked well in every area of the pitch," he said. "In the second half the team continued the same way and we were more clinical. Looking at the result it seems easy, but everything is complex and dangerous."