Real Madrid legend Roberto Carlos has revealed what he believes to be the attribute that truly separates Cristiano Ronaldo from Lionel Messi.
The World Cup winner enjoyed a career playing with some of the all-time greats, particularly with Real and Brazil, putting him in a strong position to weigh in on the never-ending debate.
Carlos himself was once in the argument for the world's best, finishing second in the running for FIFA World Player of the Year in 1997 behind compatriot Ronaldo.
Now, however, the finest Brazilian player is undoubtedly Paris Saint-Germain's Neymar - someone who Carlos believes has forced his way to the stature of Messi and Ronaldo.
"These days, when you talk about football, you talk about Neymar, Messi and Ronaldo," he told Fox Sports.
It's high praise for Neymar, even if it is from someone with a possible bias towards his countryman, as Messi and Ronaldo have had a stranglehold on the top of the game for a decade now.
But Carlos believes there is still something that separates the two legends - something that gives Ronaldo the edge.
"Cristiano has worked to improve," he said.
"When you talk about the Ballon d'Or or any other prize, it's not just any person who votes, it's people who know football, who follow the stats of the players and pick the best in the world.
"I watch him train every day and the way he works is exciting. He wants to improve every day.
"That's the difference with Messi. Leo is a phenomenon, we never talk about Neymar... but that side of Cristiano, of training, professionalism, focus, motivation, success... Cristiano has an advantage over all the others."
Now, again, Carlos isn't completely unbiased here - spending 11 years at Real Madrid will mean you're probably going to support their star over their arch-rival's.
Still, Ronaldo's work-rate has long been heralded as possibly the best in the world and has certainly been a large part of the reason he's maintained his position at the top of the game for a decade.
And if that status is beginning to fade, Carlos believes Real have no reason to worry - their next star is already on his way.
17-year-old Brazilian Vinicius Junior signed from Flamengo in the summer for an extravagant €45 million, although he's likely to remain on loan at Brazil's biggest club until 2019, and Carlos feels he's a club icon in the making.
"I'm not going to say that he's ready because he's still very young, but what Real Madrid have done, thinking about the future of the club, I think is perfect both for Real Madrid and Flamengo," said the 44-year-old of the teenager.
"He's coming to Europe to learn, to accelerate the learning process as a player and as a man.
"He knows playing for Real Madrid won't be easy because the Bernabeu is very big, the fans demand a lot. To be a Real Madrid player should make him very proud and very motivated.
"He has an even bigger responsibility today to improve day by day. I wish him a lot of luck because I'm certain he's going to become an idol within this club."
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