Optimism laced the resignation. Barcelona had been beaten for only the third time this season, but they had not yet been defeated and they felt entitled to believe they would not be either. The natural reaction might have been to insist the second leg will be different; in fact, the European champions insisted it will be much the same. If the final score needs to change, the performance need not.

Pedro lamented the fact that Barcelona had been left "looking like fools". More foolish would be to change everything. "It is a pity," Víctor Valdés said. "Chelsea had 100% efficiency, scoring their only chance. 1-0 is a dangerous result and we'll have to be careful, but if you analyse the game we created enough chances. We can be satisfied. We trust that if we play the same way in the second leg we can go through."

That analysis may conclude that although this was far from Barcelona's best performance, their possession topped 70%, they hit the woodwork twice and Sergio Busquets, Cesc Fábregas and Alexis Sánchez all missed excellent opportunities. At the Camp Nou, they must make more of them. They must also, Andrés Iniesta said, stripping the analysis to its most basic, "take them".

So Barcelona will play much the same way. But will Chelsea? Should they? Can they? One Spanish radio station asked Juan Mata the loaded question about Chelsea's "ultra-defensive" approach. He responded: "I understand that, but we had to be pragmatic. This was the way we had to approach this game; with them having lots of possession and us waiting. It was effective." Whether it will be effective in Catalonia is another issue.

Much has been made of the vast space of the Camp Nou. In fact, the pitch is only a metre wider and two metres longer than Stamford Bridge. But defending there is harder and Chelsea must decide if they are equipped to protect what they hold or if they should seek more. They may have no choice. The Athletic Bilbao defender Andoni Iraola notes that Barcelona are so dangerous that you "almost have to forget about playing". Teams do not always play the way they want against Barcelona so much as the way they can. They don't always choose to hang on. They do not always succeed either.

Earlier this season, Sevilla got a 0-0 draw there, a result that would put Chelsea through. Sevilla's approach was similar: sit deep and deny Barcelona space – accumulating bodies inside. Esteban Vigo, the coach whose Hércules side won 2-0 at Barcelona two years ago, stressed the importance of forcing Barcelona inside, making the pitch small.

Sevilla also got lucky. "You can't get a result against Barcelona here without your goalkeeper being man of the match," said their coach, Marcelino García Toral. Javi Varas's save count reached double figures and included a penalty from Lionel Messi in the 94th minute. There was something implausible about the result. Sevilla, though, had judged that parking the bus was the only plausible way.

When Internazionale knocked Barcelona out of the Champions League in 2010, they did the same. But it is often forgotten that Inter lost the second leg 1-0 and, but for the referee wrongly ruling out Bojan's late goal, it would have been 2-0, enough for Barça to win the tie.

Because ultra-defensive damage limitation has worked, it is seen as the solution. But it has failed many more times. Others have been aggressive, pressing high up the pitch. Mauricio Pochettino's Espanyol invariably do so and rarely have Pep Guardiola's team looked less comfortable. In the Copa del Rey semi-final, second leg Real Madrid did the same, chasing Barcelona down all over the pitch, pushing them deep into their own area. So used to teams waiting, Barcelona struggled. It finished 2-2, a result that would put Chelsea through.

That requires talent, organisation and energy. Nerve, too. Many coaches have decided that playing any way other than defensively is not so much risky as suicidal. Roberto Di Matteo was among them.

Getafe defeated Barcelona 1-0 this season, Juan Valera heading the winner from a corner. But as one member of the club's technical staff puts it: if they played that same game 10 times they would lose nine. Barcelona had 17 shots, Getafe one. All you can do, he admits, is minimise the chances and hope you take yours.

Chelsea did. Doing it again may be a big ask. Theirs was an impressive display at Stamford Bridge but it was also a precarious one. In the aftermath of Wednesday's win one Chelsea player shot an embarrassed smile, barely able to believe his side had got away with it. Another admitted they could not risk relying on achieving the same result in the same way in the second leg. We simply cannot hold on like that again, he confided. At the Camp Nou, Chelsea may have to score.

The advantage they have now is that it is Barcelona who have obligations and anxieties. Overcome the first wave of pressure and the pitch will open out in front of Chelsea, especially in the left channel – one that Ramires exploited so well in London. Speed on the break could be key again. Fernando Torres had expected to play in London; he will almost certainly play in Catalonia. Di Matteo sought counsel before the first leg, asking those who have stopped Barcelonça how they did it. He could ask Torres: the Madrileño has faced Barcelona 10 times and scored seven times.

"We have to try and score there," Mata said. The reasoning is simple: Chelsea expect a Barcelona goal.