Keylor Navas has arrived to provide competition for Casillas this season, but the experienced Spaniard started last week's European Super Cup against Sevilla.
"Iker will play. He's training and has the confidence of everyone. After that we'll see," Ancelotti told reporters at a press conference.
Casillas represented Madrid in both the Champions League and Copa del Rey last season, but played second fiddle to Diego Lopez, who has now moved on to AC Milan, in the league.