What an extraordinary weekend. Where do I start? Well, in Anoeta (predictably), where I witnessed quite an apocalyptic event. Stop all the clocks, cut off the telephone - Barcelona have lost a league match.
The last time they lost an away game in the league was in February 2012 at Pamplona, also up here in the murky north and by the same 3-2 score by which Real Sociedad beat them on Saturday. They seem to have problems in Anoeta, having failed to win there for the last three seasons, and even Leo Messi had never scored there - a little problem he resolved after six minutes of Saturday's game, but to no avail for his team.
The game in San Sebastián had originally been scheduled for 22.00 on the petition of Canal Plus, but the Spanish Federation rescheduled it for 18.00 after protests from the club and on social networks that it was 'Tamborradas' night - the fiesta that celebrates the kicking out of the Napoleonic troops from the city in 1813. It is among the greatest of all the weird and wonderful Spanish fiestas, up there with the Fallas in Valencia, the Tomatina in Buñol and San Fermines in Pamplona.
Tamborradas (a sort of mass drumming festival) kicks off at midnight with military precision, and the idea that the biggest game of the year against the best side in the world would only just have finished was unthinkable. It was also the bicentenary of the historical event that gave rise to the fiesta. For once, the football authorities saw sense.
Real Sociedad came back from 2-0 down and scored the winner in the 91st minute, helped somewhat by Gerard Pique's sending off after 60 minutes. But the win owed more to their enthusiasm and devil-may-care approach to the game - often a suicidal tactic against Barcelona, but on Saturday one that paid off. It would be foolish to read too much into the result - as if it gives either Atlético or Real Madrid a glimmer of hope, or signals the beginning of a period in the doldrums for the Catalans.
The truth is that they had to lose sometime, and I'm mighty happy they chose Saturday night to play with slightly less intensity than usual - not because I have anything against them but simply because, as a resident of this city for over 20 years, it would be silly to pretend I wasn't celebrating with the rest of the 30,000 who turned up.
Barcelona are popular here, for politico-cultural reasons that need little explanation, and even though certain characters in their present squad are seen as a little mouthy and a little too quick to complain when things don't go their way, San Sebastian's residents never display hostility towards them. I rushed straight to the game with my son, who had just finished his own match in Juvenil Nacional at 17.15, and as we were leaving the ground, two of his team-mates made a show of putting on their Barcelona shirts before jumping into cars en route to Anoeta. You'd never see people doing that in a Madrid shirt.
It's been said before, but the best way to ruffle Barcelona - whether or not they were tired from their exertions in the cup against Malaga three days earlier- is to try to play football against them. Sit back, park the bus and they'll pummel you into submission.
Even Real Madrid have learned this lesson, but there are no guarantees it will always pay off. Sociedad fell to two early sucker-punches and could have gone 3-0 down when Messi hit the post, but recovered from those shocks and scored just before half-time, buoyed by the fantastic pre-fiesta atmosphere and their own quality players, motivated by the occasion.
Phillipe Montanier, the French manager employed by the club because of his alleged belief in the 'Barça way', finally got the tactical approach right. His two misfiring forwards, Diego Ifran and Imanol Agirretxe, were left on the bench and he instead employed his opponents' system of a strikerless formation, a plan that seemed to ruffle Puyol and Pique from the start. Sociedad's quick offensive midfielders, Antoine Griezmann, Chory Castro and Xabi Prieto, soon began to find spaces, and 'false nine' Carlos Vela has no qualms about running at defenders, whoever they are.
The home side also employed a high line - a risky strategy that almost rebounded on them. But, as the second half wore on, it was interesting to see how much possession Barcelona lost in the second third of the pitch, hoist by their own petard. Andres Iniesta was fantastic but, apart from him, the Catalans didn't seem to have the usual fight in their bellies. When Pique walked, they tried their best to hold onto possession but were eventually overwhelmed. It was a wonderful game, and it left a warm glow around the city all weekend. People still can't quite believe what they saw.
The defeat was the culmination of a relatively negative week for Barcelona. Held to a surprising 2-2 draw in the King's Cup quarter-final first-leg by 10-man Malaga at the Camp Nou and ruffled by the news that goalkeeper Victor Valdes would not be signing an extension to his contract (it expires next June), the announcement by Bayern Munich that Saint Pep was to become their manager next season did nothing to lighten their mood.
Of course, everyone knew Guardiola was seeking employment after his sabbatical, but the odds were on his replacing Roberto Mancini at Manchester City. Now, however, there are new rumours and whispers about who he may have his eyes on or - more to the point - which potentially disaffected Barcelona players might want to join him in the medium term, especially if he proves a success in Germany.
Valdes' own decision seems unlikely to have been swayed by Pep's new choice, since Manuel Neuer is a fine goalkeeper with plenty of years ahead of him, but there are whispers about Sergio Busquets and new star in the firmament Gerard Deulofeu.
Barcelona fans were worried before about Txiki Begiristain taking over as director of football at Manchester City, since it seemed obvious that would be the precursor to Pep's arrival and then the departure of a whole swathe of La Masia orphans. As if this wasn't bad enough, his signing of a three-year contract with Bayern has left a strange feeling of discomfort in Barcelona, as if their anointed son really has left them for good and has chosen the Bavarian side because of their stability, their youth policy and the long-term possibilities they can offer him.
Manchester looked like a bit of fun. Bayern is something more serious. It's like their dad running off with another woman. Everyone thought it was just a temporary thing and that he'd return to the nest. But now he's gone and married her, pre-nups and all. How could he do that?
Well, I don't wish to comment too much on things I don't understand, but one aspect that might have swayed Guardiola's choice is the cultural make-up of Munich, a liberal and dynamic city, much like Barcelona and many of whose citizens consider themselves to be Bavarians first and Germans second. That gives Bayern a special identity and, although parallels with Barcelona might seem politically naïve, you wonder whether it didn't just influence him a little bit.
The tabloid Sport, Barcelona's equivalent to Marca, tried to shrug off the blues by announcing on their Sunday-morning cover 'No pasa nada, La Liga está ganada' (Don't worry, the league's already sewn up), which was actually a witty take on an old phrase used in San Sebastián in the golden days of the 1980s, 'No pasa nada, tenemos a Arconada', when the Spanish international goalkeeper (Luis Arconada) helped Real Sociedad to two consecutive league titles.
Sport, quite cleverly, thus alluded to the past culture of their temporary conquerors, but went on to assure their readers that Real Madrid were unlikely to get much change out of Valencia and that Atletico's pursuit was nothing to worry about either. However, as lead writer Toni Frieros pointed out, complacency is something that belongs to Barça's past. Nothing should be allowed to let it seep back into the culture.
In the end, Real Madrid put their troubles behind them, temporarily at least, by annihilating Valencia 5-0 at the Mestalla, a result all the more surprising given the home side's fury at their 2-0 midweek defeat at the Bernabéu in the King's Cup. That night, they felt referee Muñiz Fernandez had deprived them of a result - adding to the black-book history of robberies that Valencian folklore attributes to games in Madrid.
Valencia were up for it, Madrid were weakened in defence and in morale after the changing-room spat between Cristiano Ronaldo and Jose Mourinho, and everything pointed to a deepening of the crisis. Funny old game, football.
Ronaldo and Angel Di María, two players criticised by Mourinho of late, both scored twice, and Valencia only have the second leg of that cup tie this week as their last chance for revenge.
Meanwhile, Atlético won 2-0 at home to Levante, setting a record for consecutive home victories and cutting Barcelona's lead to eight points. Has the league opened up, ever so slightly? Probably not, given that Radamel Falcao is now injured and may be out for a month - but if Barça's lead were reduced to five points, I suppose we might be persuaded to believe. Whatever, Real Sociedad have reminded us that Barcelona are human, and that the beauty of football ultimately lies in its unpredictability.