After watching his side nearly blow three-goal leads twice in four days, the Italian said that he believes his players are not focused enough during games
Los Blancos had surged into a three-goal lead through Cristiano Ronaldo, who struck twice, and Karim Benzema but narrowly avoided dropping two precious points after Jonathan Viera's quick-fire double from the penalty spot.
After citing similar struggles containing Sevilla's comeback attempt in Wednesday's 7-3 win at the Santiago Bernabeu, Ancelotti demanded an end to his side's propensity for complacency.
"Conceding like we have in these past two games cannot be a coincidence," the Italian noted to reporters. "Defensively, the second half was a disaster.
"This is something I have to talk about in the locker room, but I will address it generally here. I think we need to change a little and remove the superficial attitude we sometimes have on the field.
"A team of this quality should not risk losing the match when we are 3-0 up. To think that the match is finished at 3-0 is a big mistake. This is not football.
"It has happened twice and I am sure it will not happen again."
The capital outfit stays within six points of Liga leader Barcelona but, it has already conceded 16 goals after only 12 games.