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."
Bizarre Jose Mourinho statement aims to pre-empt punishment after Fenerbahce boss clashes with Galatasaray counterpart
'Andy Robertson has a decision to make as a player, where you either roll your sleeves up and give someone great competition or you accept decisions and say that your time is done.' Alan Shearer on the conundrum facing Arne Slot's Liverpool
