Coach Carlo Ancelotti confirmed in a press conference that his club-record signing Bale will be replaced by Angel Di Maria for the Copa del Rey tie.
Ancelotti also revealed that he will look to experiment in the fixture ahead of Real's La Liga clash with Valencia on Sunday, a game that Bale could return for.
"Di Maria will play tomorrow because Bale won't be available due to a small injury he picked up today," Ancelotti said.
"Di Maria is a very important player for us.
"I don't know if Bale will play on Sunday. I think he suffered a small knock but we have to find out.
"We will decide the line up we'll use against Valencia after tomorrow's game. We have Nacho, (Alvaro) Arbeloa and (Diego) Llorente in defence.
"Xabi Alonso will be on the bench tomorrow. Our midfield will be different."
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