Iker Casillas, who has been at Real Madrid since he joined in 1990 at the tender age of nine, will leave the club to join FC Porto. It hasn’t been made official, but at this point, it is only a matter of time.

This puts an end to a complicated stand-off between the player and the club that you can read all about here. In the end, it looks like Madrid was so desperate to get rid of Casillas that it agreed to pay him 15 million euros to leave. Casillas is, without a doubt, one of the three most important Madridistas of all time, so if his exit makes little or no sense to you, I wouldn’t blame you.

It’s difficult to overstate the magnitude of Casillas at Real Madrid. The local boy from Mostoles, a large working class suburb from Madrid, he came through the club’s youth ranks and broke into the first team as a starter in 1999 at 18, He ended up starting in and winning the Champions League final against Valencia. He would win two more Champions Leagues, including an absolutely epic performance coming on as a substitute in the 2002 final against Bayer Leverkusen.

He won five leagues and was named the world’s best goalkeeper a record five times in a row. Perhaps most importantly, he captained Spain to two European Championships and one World Cup title, in 2010, with a vintage “San Iker” performance in the final against Holland.

He is, without a doubt, the greatest goalkeeper to ever play for Real Madrid.

Despite all of his greatness and all-around class attitude, Iker Casillas has been booed by a sector of the Bernabéu fans at nearly every single home game for the past two seasons. Where did it all go wrong between Casillas and Real Madrid?

It all started with a phone call in the fall of 2011 between Casillas, then the captain of both Real Madrid and Spain, and Xavi and Carles Puyol, captains of FC Barcelona. Tensions were at an all-time high between Real Madrid and Barcelona, mostly due to the unprecedented provocative sword wielding of Madrid head coach José Mourinho. Mourinho fomented an “us against them” mentality, preferring to treat the relationship with Barça as an openly hostile one rather than one based on mutual respect. He even stuck his fucking finger in the late Tito Vilanova’s eye at the end of a particularly heated Clasico.

Casillas, who at first bought into Mourinho’s brinksmanship, realized that things had gotten way out of hand, and if that he didn’t act as the captain of Spain, he would put that summer’s 2012 European championship campaign in jeopardy. He decided to reach out to Puyol and Xavi to try to calm the waters and build unity ahead of the tournament. By Casillas’s own account, the call was tense, but ultimately a key factor in Spain’s ultimate victory at Euro 2012.

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Mourinho saw this as outright treason and never forgave Casillas. Mourinho is a man who sees two kinds of people in the world: those who are with him, and those who are against him. He started to suspect that Casillas was against him.

When things started to go south for Mourinho at Real Madrid, the coach grew increasingly paranoid. By the end, nearly everyone on the squad, including his former Caporegimes and fellow countrymen Cristiano Ronaldo and Pepe had turned on him. Mourinho thought that the root of it all was Casillas. He began a sustained and orchestrated propaganda campaign through media outlets that were friendly to him, accusing Casillas of being a topo (mole). He suspected that Casillas was filtering the inner workings of the squad to the press. It did not help Casillas’ cause that his wife, sports journalist Sara Carbonero, went on Mexican TV in early 2013 and said that the players “just couldn’t stomach Mourinho.”

Mourinho’s general “us against them” mentality had a deep appeal among a hardcore sector of Madrid’s fans, especially those that see the Madrid-Barça rivalry as part of the broader culture war raging right now in Spain. The tension between Madrid and Catalunya is at an all-time high. The country is caught in a vicious cycle of chest bumping in which one side’s nationalistic provocations simply fuel the other’s sense of national fanaticism. In this context, Mourinho’s constant provocations against not just Barça but the idea of Barca was irresistible red-meat to the more fervent, Spanish flag-bearing Madridistas.

Iker Casillas is a victim of this culture war. Within it, he’s seen as a traitor to the cause. That’s a ridiculous and ugly conclusion, but it’s the way it is.

No one knows this better than Casillas, who has withstood the abuse in elegant silence. The club has not given him a hand, mostly because president Florentino Pérez was never a huge fan of his. (It’s an open secret that his dream was always to sign Juventus’s Gigi Buffon.) Pérez is generally suspicious and probably envious of players that garner too much power at Real Madrid. It is why he’s currently at war with his three most powerful players.

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So now Pérez is finally getting his way, even though it’s going to cost him. Once again, he’s managed to unceremoniously boot out a club legend. In a summer where players like Steven Gerrard, Xavi, and Andrea Pirlo were given legend’s farewells, Casillas is getting thrown under the bus. But that’s the way it always seems to be with Florentino, whether your name is Redondo, Hierro, Del Bosque, Figo, Raúl, Xabi Alonso, or Sergio Ramos.

So who will replace Casillas at Real Madrid?

Well for a while it seemed like a foregone conclusion that Manchester United’s David de Gea would replace him. De Gea is so homesick that he is willing to forget the fact that he is a lifelong Atléti fan in order to be closer to his girlfriend and family. He only has one year left on his deal, so it looked like United would eventually be forced to make a deal. That is until the Sergio Ramos situation at Real Madrid exploded and threw a serious wrench in the negotiations.

There is a dearth of world-class center backs these days, and Manchester United simply cannot pass up on an opportunity to sign arguably the best one in the world. Because Ramos has officially requested a transfer to United, its negotiating position vis-á-vis de Gea is much stronger.

That is why, in the last two days, Real Madrid has seemingly done a dramatic about-face and is close to signing Espanyol’s Kiko Casilla. That’s right, there’s a strong possibility that Iker Casillas will be replaced by a guy who’s name is the same, minus an ‘s’.

Casilla is actually a product of Real Madrid’s youth system and was always considered one of the best goalkeeping prospects of his generation. He’s a totally different style of keeper than de Gea — more of a commanding presence in the area due to his enormous size rather than a quick shot stopper.

His strong performances for Espanyol have put him on the Spanish national team’s radar, with his international debut coming last season in a friendly against Germany.

Whoever comes to replace Iker Casillas will be stepping into a penalty box owned by a club legend for the last 16 years. It won’t be an easy task for whomever is chosen. It takes a special kind of mental strength to withstand the pressure of being Real Madrid’s No. 1.

In the end, that was what made Casillas so special. He managed to make the extraordinary ordinary, no matter how adverse the situation.