Flick's tactical approach, featuring an extremely high defensive line, also seemed ripe for Mbappe and Vinicius to pillage with their pace.
"Real Madrid strongly condemns any kind of behaviour involving racism, xenophobia or violence in football and sport, and deeply regrets the insults that a few fans uttered last night in one of the corners of the stadium," said Los Blancos in a statement Sunday.
"We are hurt, it's a tough moment, but I want to thank the fans for their support. We don't have to throw everything away, because there is nothing to throw away," added a downhearted Ancelotti.
The Catalan giants triumphed at the Santiago Bernabeu to snap Madrid's run of 42 matches unbeaten and continue their own revival under the German coach who arrived this summer.
Robert Lewandowski struck twice in two minutes as Barcelona crushed rivals Real Madrid 4-0 on Saturday, inflicting the Spanish champions' first La Liga defeat in over a year.
Defending champions Real Madrid are set to host archrivals Barcelona in a LaLiga game at the Santiago Bernabeu tonight.
Kylian Mbappe's start at Real Madrid has been satisfactory, his performances neither spectacular nor underwhelming, but Saturday's La Liga Clasico offers the French superstar a springboard to kick on from.
The viral social media campaign before the September 29 clash encouraged Atletico fans to arrive at the club's Metropolitano stadium and utter "degrading and discriminatory insults with racist connotations" against a Real player, police said.
Real Madrid duo Thibaut Courtois and Rodrygo are likely to miss the Clasico clash with La Liga leaders Barcelona on Saturday with injury problems.
Former Real Madrid goalkeeper Iker Casillas has labelled Barcelona star Lionel Messi the opponent he has had the most difficulty facing.
Lionel Messi posted a cryptic Instagram message on Friday as he continues his recovery from a knee injury.