What is a hero without a villain? Whichever side you sit on in the great Clasico divide, or even if you are a neutral, one thing is for certain: Real Madrid versus Barcelona simply will not have the same spice without Cristiano Ronaldo against Lionel Messi.
The Portuguese and the Argentine have dominated modern football, winning the past 10 Ballons d'Or between them and pushing each other onto new levels. While there is respect off the pitch, they are desperate to beat one another on it.
There has always been the sense that the rivalry means more to Ronaldo. He has spoken of wanting to be better than Messi, of catching his Ballon d'Or tally and more, while Leo only really praises Cristiano when he is asked about the now former Madrid man.
Nevertheless, it is a battle that clearly matters a lot for football fans and supporters of the respective clubs. So much so, in fact, that is has led to the tired and constant debate about which player is better.
On the pitch, however, it has always been fascinating. In the earlier years, during Pep Guardiola's time in charge, Barca and Messi had by far the better of their meetings, while in recent years things have been more even, with success for Real and Ronaldo too.
The rivalry is unique in football history. In the past, many have spoken about Pele and Diego Maradona, but those two played in different eras and never against one another. Ronaldo and Messi, though, were the two finest footballers of their generation, representing the world's two biggest clubs, in the same league. For nine whole years.
It has been spectacular and always made meetings between Barca and Madrid more interesting. And it was not just the Clasico, either, because the presence of these two titans ensured there was some stardust in every game played by Spain's top teams.
Now, with Neymar gone last summer and Ronaldo officially departed to Juventus on Tuesday , La Liga has lost some of that star quality. Messi and Cristiano can still meet in the Champions League, of course, or on stage at the Ballon d'Or or The Best ceremonies, but things will never be the same.
"They have been nine unique years," Ronaldo said in an open letter to the Real Madrid fans on Tuesday after his move to Juventus was confirmed. "It has been an exciting time for me, full of consideration but also hard because Real Madrid is of a very high demand, but I know very well that I will never forget that I have enjoyed football here in a unique way.
"I have had fabulous team-mates on the field and in the dressing room, I have felt the warmth of an incredible crowd and together we have won three Champions Leagues in a row and four in five years.
"And with them also, on an individual level, I have the satisfaction of having won four Golden Balls and three Golden Shoes. All during my time in this immense and extraordinary club."
There was, of course, no mention of Barca or Messi. But Ronaldo relished facing the enemy. From his iconic "calma" gestures at Camp Nou, to his shirt celebration copying Leo's at the Bernabeu, to his header in the 2011 Copa del Rey final, pushing Pep, the referee and so much more, Cristiano in the Clasico was always a thrill.
Messi has had countless Clasico memories in that time, too, and the match-up always made for must-watch drama, while their presence meant dominance in individual awards and also club trophies, with Barca and Madrid the teams to beat in Europe over the past decade.
“You have to remember that Real Madrid and Barcelona have a magical appeal to players all over the world and can generally sign who they want, but they have had Cristiano Ronaldo and Lionel Messi at their peak for the last few years, which has been a deciding factor in so many big games," former England striker Gary Lineker said in March.
“The two of them are now getting towards the back end of their careers, and when they go, which sadly for all of us they will, it is going to be impossible to replace them. The exits of Ronaldo and Messi will level things quite significantly because those two players have been so far above everyone else in the world game for an extended period of time.”
Ronaldo is the first to go and his loss will be felt greatly, not only in the Clasico, but every time Real take to the field, whoever comes in to replace him. Cristiano at Juve will be another captivating chapter, but his departure leaves a big hole and the next Barca-Madrid match will be very strange indeed. It really is the end of an era.