The Portuguese has been linked with a move to former club Manchester United in recent weeks, with a group of fans from the Premier League club organising for a banner to be flown over Real's clash with Villarreal on Saturday, pleading for his return.
Ancelotti has now heaped praise on the attacker, describing him as the best player he has ever coached.
"Cristiano is a very professional and serious player," he said. "He is a leader who doesn't talk much but is an example for everyone.
"Cristiano is the best player I've ever coached in my career."
Real face Ludogorets in the UEFA Champions League on Wednesday, and Ancelotti says it would be foolish to write off the Bulgarians, who suffered a narrow 2-1 defeat at Liverpool a fortnight ago.
"There are no modest teams in this competition," he insisted. "Everyone is fighting to win."
Attacker Isco echoed those comments, adding: "We respect our opponent but we want to win and become group leaders.
"This is a very important game in a difficult stadium. I hope we continue our winning streak.
"I know that Ludogorets caused Liverpool problems at Anfield. The coach has shown us some videos."
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