Jose Mourinho spent three seasons at the reign of Real Madrid when he took over Manuel Pellegrini in May 2010.
It was during his tenure as the eleventh manager at the Santiago Bernabeu that he spent his time with Cristiano Ronaldo.
During that relationship, Real Madrid won the La Liga and the Copa del Ray, with Ronaldo collecting an incredible 120 goals.
The success of the partnership began to suffer at the end when tensions were reported to have arisen towards the end of Mourinho’s time as head coach.
However, the Portugese, who has returned to Chelsea as its boss, insists that Ronaldo is one of the most professional players in the world.
"Coaching (Ronaldo) was the highlight of my career," Mourinho was reported in saying to newswires. "He's the most professional player I've ever met.
"A coach and player may have their differences at a given time, but it ends there. I don't have any problem.
"I had only one problem with him, very simple, very basic.
"When a coach criticises a player from a tactical viewpoint trying to improve what in my view could have been improved.
“And at this moment he didn't take it very well because maybe he thinks he knows everything and the coach cannot help him to develop anymore."