Bale has hardly featured under Zidane since the season restarted and has appeared disinterested when watching with his team-mates.
Asked about Bale’s absence for the Champions League last-16 second leg against City, Zidane said: "I'll explain. Many things have been said. We have a respectful coach-player relationship. The only thing I can say is that he preferred not to play. Nothing more. The rest is between him and me.
"He’s not injured. I really respect him and all the other players. Things that happen in the dressing room stay there."
Reuters say a source close to the player said Bale did not wish to travel to the game because he believed he was not going to play any part in it.
Although Bale does not seem to feature in Zidane’s plans, he has two years left on his contract and seemingly does not wish to leave despite his lack of minutes.
"Gareth is fine," his agent Jonathan Barnett told the BBC recently.
"He has two years left on his contract. He likes living in Madrid and he is going nowhere."