Ronaldo attended a gathering to celebrate his birthday hours after playing in Real's 4-0 thrashing at fierce rivals Atletico Madrid on Saturday, and a number of the club's fans expressed their displeasure at training on Monday.
Jorge Mendes, Ronaldo's agent, jumped to his client's defence, as did ex-Real and Portugal captain Luis Figo.
And now Ancelotti has weighed in to the debate, challenging anyone to question the attitude of Ronaldo.
"I should write a book, or at least, a long chapter on him," he told A Bola. "Cristiano is a player with an efficiency that is unique in today's football.
"He has an extraordinary talent and he enjoys it with such a professionalism and seriousness that is difficult to find in a player of that level.
"In the changing room he is the leader. He speaks a lot to his team-mates, especially to the young ones.
"He is a very important figure, just like Pepe, Sergio Ramos, Iker Casillas or Marcelo.
"If he continues to feel the passion that he has for what he does, he can continue until who knows when, thanks to his great physique and unique genetics."
