Camp Nou, a cathedral of Catalan nationalism as well as the home of FC Barcelona, turned separatist at the match between Barça and its historic Spanish rival, Real Madrid. At 17 minutes and 14 seconds into the game - to mark Catalonia's defeat by the Spanish crown in 1714 - the stadium-wide mosaic of the traditional national flag, the Senyera, flipped over into the starred flag of Catalan separatists, ubiquitous since a vast secessionist rally occupied Barcelona in September.
The football itself ended in a well-fought 2-2 draw, a fair reflection of the constitutional battle between Catalonia and the rest of Spain. But it was foreigners - Lionel Messi for Barça and Cristiano Ronaldo for Real Madrid - who scored the goals for each side.
Foreigners may also help determine the outcome of the increasingly shrill struggle between Barcelona and Madrid over whether Catalonia has a future inside Spain - at least if the Generalitat, Catalonia's autonomous government, has its way.
Already, Catalan leaders are highlighting how the British government has calmly agreed to a Scottish referendum on independence, arguing over the details of the plebiscite rather than Scotland's right to decide its own future.
They now intend to plead their cause across the EU and beyond, even though the Spanish government has warned them their plan to call a vote on Catalonia's future violates the constitution.
The first step is the Catalan election in November, called early by Artur Mas, president of the Generalitat, after Mariano Rajoy, the Spanish prime minister, refused even to discuss Catalonia's demands for fiscal autonomy - the right to collect its own taxes as the Basques already do.
Mr Mas hopes to win a majority for his mainstream nationalist Convergencia i Unio party. But along with the surge in separatist sentiment, and with much of the Catalan left acknowledging the right to self-determination while defending a federal model, there is little doubt Mr Mas will have the democratic legitimacy to call a referendum.
Barcelona will then seek Madrid's constitutional authorisation to hold a vote. But Mr Rajoy's centre-right Partido Popular (PP) government has already ruled this out, as both sides exchange volleys of bilious rhetoric. The new Catalan parliament is therefore expected to pass its own law, mandating a "consultation" - a referendum by another name.
A chorus of PP leaders and ministers has warned that if it comes to that they will use the full force of the law to abort any vote, up to and including suspending home rule and banning Mr Mas.
By then, however, the Catalans hope to have internationalised the dispute, against the backdrop of Scotland's vote and the gathering strength of Flemish separatism in Belgium. "How are they going to explain this in Europe when all we want to do is vote?" says a senior Catalan leader.
"The [Spanish] state has to see this process as one of emancipation", Mr Mas said revcently. "There are natural laws and it is up to the legal framework to adjust to democracy". He is due in Brussels early November to make this case.
The push for independence he is spearheading started in 2010, after the constitutional court eviscerated reforms legislated in 2006 enhancing Catalonia's statute of autonomy, even though they had been endorsed by both the Catalan and Spanish parliaments and in a referendum sanctioned by Madrid.
The eurozone and fiscal crises have made separatism even more mainstream, exacerbating long-standing grievances: in particular, that relatively wealthy Catalonia hands over a disproportionate amount of its income to a state that has stopped investing in its infrastructure. "After China, Spain has the second largest high-speed train network in the world, but we are still not connected to France," says Heribert Padrol, a tax lawyer who advised Mr Mas on fiscal autonomy.
Catalan strategists plan a campaign that is "peaceful, orderly, and impeccably democratic", as one puts it. The feeling that the status quo is no longer tenable stretches well beyond the increasingly indistinguishable nationalist and separatist camps.
Mr Mas has set out on a path that could lead to deeper self-government rather than secession. But since almost no one in either Barcelona or Madrid expects Mr Rajoy to copy British prime minister David Cameron's stance on Scotland, the same path leads to independence. It will simply be longer and more tortuous.
Andreu Mas-Colell, the Harvard economist and Generalitat's finance chief, points out that after the vast separatist rally, everyone's room for compromise has narrowed. "If they come back to us on the fiscal [autonomy] pact - and I don't think they will - the demand for a referendum cannot now be withdrawn."
A business leader who, like many of his nervous peers believes Catalonia is being left behind but fears a leap in the dark, and was for fiscal autonomy but against secession, concurs. "We need a radical redesign that reflects the reality of Spain - Spain needs to do this for itself, not to satisfy Catalonia."
"It would be a giant step for Spain to treat all this as just one more issue in the political debate", like the UK does with Scotland or Canada with Quebec, says Mr Mas-Colell. "It's not that they think Catalonia is Spain," adds an aide to Mr Mas. "They think Catalonia is Spain's."