Real Madrid full-back Marcelo insists there is "no doubt" that Cristiano Ronaldo is the best player in the world.

Ronaldo is favourite to scoop his fourth Ballon d'Or in January after helping Madrid and Portugal to Champions League and Euro 2016 glory respectively this year.

The 31-year-old responded tersely to ex-Barcelona midfielder Xavi stating Lionel Messi remains the world's premier footballer, and Marcelo believes the number one is in the same colours as him.

Speaking ahead of Madrid beginning their Champions League defence against Ronaldo's boyhood club Sporting CP, the Brazil international said: "Everyone wants to talk about Ronaldo. I see him work every day and I think he's the best.

"It isn't just what I think. I think it's what many people believe.

"He's won three Ballons d'Or and he works really hard for the team.

"There is plenty more to come from Ronaldo. He's is still young and he's a great team-mate.

"He is number one in the world, there is no doubt."

Madrid will aim to become the first team of to retain the Champions League since the competition rebranded from the European Cup and adopted a group-stage format, having won a record 11th title at the expense of city rivals Atletico Madrid last season.

"We've got to try and build on last season," Marcelo said. "It's is still early days with our objectives that we are trying to accomplish.

"It will be a tough season, just like last season. It is not easy to win the Champions League but we are on the right path.

"We're here, we're taking part so, yes, there is a chance [Madrid will win] like all teams who are taking part in the tournament.

"No team has won successive Champions League titles but our job is to try and win the Champions League."