However, Karanka refused to comment on the speculation despite praising the winger.
"Bale is another team's player and I can not say anything about him," Karanka told reporters. "He is a classy player though."
Jose Mourinho's assistant also went on to speak about the centre-back situation at Madrid, with Pepe seemingly having lost his place to youngster Raphael Varane.
He continued: "Pepe is important for us and will continue to be important. He is still coming back from injury.
"If anyone is happy for Varane, it's Pepe."
Madrid's next match is against Celta Vigo tomorrow evening.