Bale was rested for Saturday's 3-0 La Liga win over Eibar because of a knock.
But the Wales forward has shaken off that problem and is in line to feature as Real aim to seize the initiative against a side they beat 4-1 in last year's final.
"Gareth Bale is in good shape, I have a fully fit squad," Real coach Carlo Ancelotti said.
"Gareth Bale had a fantastic season last season and is having a really good season until now. The key to his unbelievable season last year was that he scored in the Copa del Rey and Champions League final. He will be important like he was last year."
Real are winless in their six meetings with the Liga champions this season and Ancelotti is under no illusions as to what it will take to end that run.
"Of course they're a tough team. Defensively they are very strong and they've played well against us in the last few meetings. It's a team we respect," he added.
"They fight from the first minute until the last minute. I want to see my team compete and fight until the very end. That's what I'd like to see from my players."
