For those who have followed Jose Mourinho's glittering career closely, his time at Real Madrid felt like a turning point.
It was in 2013, three years after arriving wide-eyed at the Bernabeu, that something snapped.
The Portuguese had fallen out with the big guns in the dressing room, Pepe, Sergio Ramos, and Cristiano Ronaldo all having been alienated.
Off the pitch, his relationship with the Spanish media took its toll. He wanted to be "where people love me" and it was little surprise that he sought solace in a return to former club Chelsea.
That final season in the Spanish capital ended trophyless. Despite having temporarily overhauled Barcelona as the dominant team in La Liga in 2012, it was a short-lived power shift and normal service was quickly resumed.
Mourinho's rivalry with the Blaugrana was deeply personal. They had turned him down in favour of Pep Guardiola and had inflicted the greatest defeat of his managerial career - by a resounding 5-0 scoreline at Camp Nou - in 2010.
The tension between the two clubs was palpable and to be honest, unsavoury.
In an interview with La Sexta, Andres Iniesta has been recalling how Mourinho shaped El Clasico during his time with Real - and the former Barcelona midfielder had nothing positive to say.
Mourinho was to blame
"You don’t have to be for Barcelona or Real Madrid to know that the situation was unpleasant," Iniesta said.
"And the key component in that story was Mourinho. Whoever doesn’t want to see that, is radical.
"You didn’t see the rivalry that always existed before. It went beyond that. You saw hate. That atmosphere developed and it was unbearable."
There were ramifications for the national team, too. The last year has seen renewed difficulties for Catalans in La Roja's set-up in light of the independence referendum, yet Iniesta believes Mourinho also did his fair share of damage too.
"The Barca-Madrid tension caused by Mourinho did much damage to the national team and the teammates," he added.
There are, of course, two sides to every story and Mourinho has often lamented the way he was treated in Spain.
Sections of the Madrid crowd whistled him at every opportunity and he never enjoyed the same rapport with the media that we have seen in English football.
Manchester United fans might wonder, nonetheless, whether the scars of that hateful period of his career are still engrained somewhere in his psyche.
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