The club confirmed earlier on Tuesday that Marcelo would be sidelined with a hamstring tear, prompting some to suspect that Bale could drop back to the position he occupied in the early days of his career when Real take on Borussia Dortmund in the UEFA Champions League quarter-finals on Wednesday.
However, when questioned on the matter, Ancelotti insisted: "No, Gareth Bale will play forward."
The Italian has opted instead for Fabio Coentrao to continue with the role filled in Real's 5-0 demolition of Rayo Vallecano on Saturday, and revealed he had had 24 hours to mull over the decision.
"We knew yesterday," he said. "Fabio Coentrao is ready to come in. He is fresh and hasn't played many games. We will cover the loss well.
"Marcelo and Coentrao have the same job, so nothing really changes."
Real and Dortmund met in the semi-final of last year's tournament, with the German side progressing to the final, and Ancelotti has watched the games back in preparation for this week's encounter.
"I watched the games against Dortmund from last season," he continued. "They were strange matches.
"I thought that in the first leg Madrid had good control in the first half. The second half was incredible.
"In the UEFA Champions League things like that can happen. We will need to play with a lot of intensity."
Ancelotti also stressed winger Cristiano Ronaldo had "forgotten" the jeers he received during Real's clash with Rayo Vallecano at the weekend.
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