Cristiano Ronaldo and Gareth Bale's rivalry has somewhat eclipsed the former's with Lionel Messi in recent years.
Ever since Bale completed his £86 million move from Tottenham to Real Madrid in 2013, becoming the world's most expensive player in the process, he's been forced to compete with his Portuguese teammate to become top dog at the Bernabeu.
Various reports over the years have suggested there's a rift between the two wingers, whilst others insisted they're competitive but get on well.
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If there's one man who can shed some truth on the matter, though, it's Carlo Ancelotti, who managed the pair during his two-year stay in Madrid.
Ahead of Portugal and Wales' Euro 2016 semi-final clash on Wednesday, in which Ronaldo and Bale will both take centre stage, the Bayern Munich manager has revealed just how fierce their rivalry is.
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Writing for the Telegraph, he said: "Gareth Bale and Cristiano Ronaldo have faced each other more times on the training ground at Valdebebas in Madrid than they can probably remember.
"Let me tell you, even when the big names at the club are playing a game at the end of training, they want to win.
"Yes, I have seen these two boys sweating over an eight-a-side game many times during my two years at Madrid. All the great players are competitors.
"They all want to come out on top even when the only thing at stake is to be able to walk into the training ground canteen as the winner.
"So when it comes to the game in Lyon, just think what it will mean to these two lads to do it for their countries."
The best want to be, well, the best - who would have thought it.
It's widely expected that Portugal's highly-anticipated clash with Wales will be decided by who performs better out of Ronaldo and Bale, with a place in the Euro 2016 final at stake.
Ronaldo and co. - incredibly - are yet to win a game in normal time en route to the semi-finals having beaten Croatia with an extra-time winner and Poland on penalties.
Wales, on the other hand, have been nothing short of sensational in France having finished top of Group B and beaten Northern Ireland and Belgium thereafter.
Chris Coleman's side will only hope Bale can continue his fine form and add to the three goals he's scored so far at the Stade des Lumieres.
They'll also pray Ronaldo has an off night, of course.