Jose Mourinho once gave Cristiano Ronaldo a dressing-down so fierce that the legendary forward was left in tears, Luka Modric has revealed.

Ronaldo, now 40, thrived on the pitch under Mourinho, 62, during their blockbuster three-season spell together at the Santiago Bernabeu, despite a notoriously fractured relationship off it.

The Portuguese superstar scored a remarkable 168 goals in 164 appearances under the self-styled 'Special One' after a slow start in Madrid, helping Mourinho win three trophies across his first two seasons.

Despite his prolific role in an explosive front three alongside superstars Karim Benzema and Angel Di Maria, Mourinho was famously critical of Ronaldo's defensive work ethic.

And now, Luka Modric, who was signed from Tottenham by Mourinho in 2013, has given an insight into one particular row that left Ronaldo in tears - all because he failed to track his runner.

'I saw him make Cristiano Ronaldo cry in the locker room,' the Croatian midfielder told Italian outlet Corriere della Sera. 'A man who gives his all on the pitch, because for once he didn't chase the opposing full-back.'

Modric, who anchored a star-studded midfield alongside Kaka and Mesut Ozil after his major £33million arrival, did not specify the exact match in which the confrontation took place but it is remiss of one high-profile incident.

Spanish football journalist Guillem Balague claimed in his biography of Ronaldo that the forward and Mourinho almost came to blows after the Madrid manager furiously chastised him in the changing room after a 2-0 win against Valencia in January 2013.

Mourinho is said to have been incensed at Ronaldo's reluctance not to track back during the game. And the superstar reportedly responded: 'After everything I've done for you, this is how you treat me? How dare you say that to me!' 

In the coming months of what proved to be Mourinho's final season at the club Ronaldo was asked repeated questions about his manager's future. 'It doesn't matter to me,' he once responded. 'What matters to me is my future and the club.'

It marked a stark contrast to the relationship they had built just months prior, when Mourinho declared before the 2012 Ballon d'Or race: 'If Messi is the best on the planet, Ronaldo is the best in the universe!'

After Mourinho's departure from the Bernabeu, he then appeared on Spanish television to address what caused relationship breakdown from his point of view.

'I had only one problem with him,' he said. 'Very simple, very basic, which was when a coach criticises a player from a tactical viewpoint trying to improve what, in my view, could have been improved.

'At that moment, he didn't take it very well because maybe he thinks he knows everything and the coach cannot help him develop further.'

Mourinho also once said their relationship did 'not exist', however, time appeared to heal their rift as he admitted years later that coaching Ronaldo was the 'highlight of my career'.

Ronaldo, too, appeared to have warmed to Mourinho in the years later, saying he was the best manager he had ever worked with - even ahead of Sir Alex Ferguson. 'I would put him at the top, I always say that,' Ronaldo said.

Despite Modric's first season at Madrid being trophyless, the midfielder was so impressed by Mourinho that he echoed the Portuguese's own iconic assessment of himself.

'Special. As a coach and as a person,' Modric said. 'He was the one who wanted me at Real Madrid. Without Mourinho, I would never have arrived. I'm sorry I only had him for one season.'

The midfielder spent a total of 13 years at Madrid - most of which were managed by Carlo Ancelotti - and is now at AC Milan and managed by Massimiliano Allegri. But he insists Mourinho is the 'toughest' out of all three. 

He added: 'Mourinho is very direct with the players, but he's honest. He treated Sergio Ramos and [new signings] the same way. If he had to tell you something, he'd tell you. Max is like that too: he tells you to your face what's right and what's wrong. Honesty is fundamental.'

Modric also weighed in his on the age-old question of Lionel Messi vs Ronaldo, but admitted he doesn't enjoy the debate.

'That's a question I don't like,' he said. 'They defined an era. I'm closer to Cristiano because I played with him, he was my teammate at Madrid, and I assure you he's not just a great footballer; he's an incredible person. People don't know it, but he has a huge heart, always ready to help others. And he's a simple, normal man.'

He added: 'I don't know [Messi] as a man, but I have no doubt he's extraordinary too. As a player, he's magnificent.'