The Portugal captain is the big favourite to claim the Golden Ball after winning the Champions League and Euro 2016 and his coach says he is the obvious choice
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Ronaldo helped Real claim the Champions League in May before going on to win Euro 2016 with Portugal in France over the summer.
The 31-year-old is the favourite to win the award and Zidane says he thinks Ronaldo is the obvious choice.
"If you look back over the course of the year, and you look at what Cristiano has achieved, it's impressive," he told reporters.
"What he's achieved in 2016, not just on an individual basis, but for his team and his country has been magnificent.
"There's been hard work from him but he knows there's always hard work from his team-mates [as well].
"I was asked about this the other day and I said he deserves to win the Ballon d'Or, clearly."
Next up for Ronaldo and Madrid is a trip to 13th-placed Alaves, but Zidane urged caution ahead of the clash.
He added: "We know that if we want to win something come the end of the season, we need to be fully focused and maintain concentration in each and every game.
"It's what we've been doing and it will help us achieve great things.
"We can't just turn up thinking it will be an easy game, we have to work. I think we've had a good week, we've trained well but no two games are the same."