They like their nicknames in South American football, as we know. But the former Argentina manager Marcelo Bielsa, who takes his remarkable Athletic Bilbao side to Old Trafford tonight, could be forgiven for not liking his much: he is "El Loco" (The Mad One).
It is the madness that comes with being completely apart and alone, usually in Bielsa's case with a stack of football videos for company. And yet, should Pep Guardiola swap the Nou Camp for Stamford Bridge, this lawyer with his glasses hung round his neck, like Larry Grayson in a tracksuit, could well succeed him as manager of Barcelona.
He would have the support of Guardiola, who reportedly once drove through the night to question him on the principles of coaching, and he has already been given the backing of perhaps the most influential figure at Barça, Lionel Messi.
Messi, like Bielsa, is from Rosario, the third city of Argentina, which dominates its vast agricultural interior. Agricultural regions are rarely hotbeds of revolution but Rosario was different in the days when it was in a ferment of Peronism, that strange mixture of union power, working-class rhetoric and right-wing posturing, glamorised for ever by the musical Evita.
By the time the young Marcelo Bielsa was disobeying his father and not just supporting but starting to play for Rosario's main club, Newell's Old Boys, at left-back, the army decided it had endured enough of this and put its tanks on to the streets of Buenos Aires. Unlike the Peronists, the junta knew exactly what they stood for. To a man, they were card-carrying fascists.
Bielsa was probably confirmed in his radical views the day his elder brother, Rafael, "disappeared". Rafael ended up in El Castillo, one of the junta's most notorious torture centres, and was eventually exiled to Spain. Perhaps not surprisingly, Marcelo studied law.
The other dictatorship Bielsa has always fought against is what he calls "the dictatorship of results", a regime that oppresses Chelsea. After a knee injury forced him out of playing, he became obsessed with tactics and the need to win well. His signature formation is a 3-1-3-3 designed to press teams hard.
In the November rain, at Bilbao's soon-to-be demolished San Mames, they met Barcelona full on. "They came at us like beasts," said Guardiola afterwards. "I have never played a team that were so aggressive and who denied us so much space." Appropriately – given that the Basques call the San Mames "The Cathedral" – Guardiola called it a "hymn to football". It finished 2-2.
Bielsa's search for perfection reached its peak when he was made manager of Argentina. It was 2002, the army was gone, the Peronists were back, brother Rafael was a few months away from being appointed Argentina's foreign secretary.
Marcelo would be radical, refusing to pair Gabriel Batistuta and Hernan Crespo as the media demanded and falling out with Javier Saviola. They flopped in the 2002 World Cup, but by trusting young talents like Javier Mascherano and the urchin from the tower blocks of Fuerte Apache, Carlos Tevez, he took Argentina to the gold medal at the Athens Olympics. Then he walked away, returning to take Chile to South Africa in 2010.
Athletic Bilbao was a strange club choice for him. Founded by shipyard workers from Sunderland, it has a tradition of direct football: its centre-forward, Fernando Llorente, is a kind of Spanish Shearer. It has only ever signed Basques. He began, naturally, with a tactical revolution, changing Bilbao's whole style of play ... as United will see tonight.