Sometimes football really is life. On Tuesday Barcelona face Chelsea in the Champions League at Stamford Bridge where in 2009 Andrés Iniesta scored a last-minute goal that he still watches occasionally. “It’s a moment that is always there, forever,” he says. For some fans, reminded of it daily, that is especially true. According to a spokeswoman for the maternity ward at the Quirón hospital in Catalonia, his goal didn’t only take Barça to the final, it provoked a spike in the birth rate. “I’m going to have to get more staff in if they keep winning titles,” Mercedes Rodríguez joked.

Nine months after Iniesta’s goal, Rodríguez noted that births were up from nine or 10 a day to 14 or 15 in her hospital alone. “People asked if there had been a full moon or something,” she said. Some reports claimed a 45% increase, which seemed unlikely, so it was tested. A study in the British Medical Journal admitted to potential “bias owing to the effects of the adjacent jubilation” of Barcelona-supporting researchers and was quick to note that they “didn’t contribute to the observed effect”, but tentatively concluded that it was plausible to talk of a 16% rise. More research, though, was needed.

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“The heightened euphoria following a victory can cultivate hedonic sensations that result in intimate celebrations, of which unplanned births may be a consequence,” the report said. “Validation of our results could contribute to a better understanding of human behaviour, improve healthcare planning, and even aid government policy makers in stimulating or reducing birth rates. Ideally, to bridge the gap between observational and trial data, it would help greatly if Iniesta were willing to replicate his intervention, although the cost of such a study could be prohibitive, not to mention harmful to the reference group [Chelsea].”

Maybe an opportunity arises now. It won’t be the same, of course – this is not a semi, for a start – and a long time has passed. Over the next few weeks, Iniesta’s “children” will celebrate their ninth birthday. Many of those players have gone, although Sergio Busquets, Gerard Piqué and Leo Messi are still around, as is Iniesta. At 33, he has already started more games this season than he did last, recovered by Ernesto Valverde, and he will start on Tuesday. “It will be very special,” he told El Mundo Deportivo. “And very hard: we’ll have to play well.”

Facebook Twitter Pinterest Ernesto Valverde has revived Barcelona by putting an extra man in midfield and making them harder to break down. Photograph: Alejandro Garcia/EPA

Piqué delivered a warning. “The expectations are always huge: whenever you play for Barcelona you’re favourites,” he said. “I know there is a favourable atmosphere, that things look good, but you have to be prudent: we must tread extremely carefully, with ‘feet of lead’ because one bad result can mean a very good season isn’t so good.”

Piqué knows things can change fast. In fact, his line about expectations always being huge may not be accurate. If a lot can change in eight years, the same is true of six months. As this season began, Barcelona were in crisis. It wasn’t just that Neymar had gone, it was how he had gone, 16 days after the vice-president said he was “200% sure” he wouldn’t leave and 11 days after Piqué announced “he stays”. It was the sense of impotence and decline, that everything was wrong. Neymar had left and Philippe Coutinho still hadn’t come. Ousmane Dembélé had but he had got injured and so had Paulinho, but few had faith in a 29-year-old arriving from China. Piqué sat on the bench at the Santiago Bernabéu watching Real Madrid complete a 5-1 aggregate victory over Barcelona in the Super Cup. Cameras caught him muttering: “Bloody hell, these guys are leading us a dance.” After the game he admitted that for the first time since he had been back at Barcelona, in 2008, he felt “inferior” to their rivals.

Now, six months on, they stand top of the table, 20 points ahead of Madrid (having played two games more) and unbeaten in the Champions League, favourites against Chelsea. This is perhaps Barcelona’s worst spell of the season: they were beaten at Espanyol in the cup on 17 January. They scraped past Alavés 2-1 with two in the last quarter of an hour on 28 January and on Saturday they only just defeated 10-man Eibar 2-0, Jordi Alba adding a late second after Luis Suárez had scored an early opener. Between those two games, they had dropped four points in two weeks, allowing Atlético to climb closer to them in the league.

Yet this season has been remarkable. Victory at Eibar, against a team that had more shots and as much of the ball, took them to 31 consecutive league games without defeat, 24 of them this season – a new club record. If there is, as ever, a debate about the style, there are few doubts about the success; and if it’s true that with Messi you always have a chance, and that Marc-André ter Stegen has often saved them, this still came as a surprise.

Valverde appeared to have arrived at the worst time but, universally admired, if there is a man to keep his head amid a crisis it is him. Calm in bad times and good, adept at managing pessimism and euphoria, he has experienced both but never changes.

“He was clear from the start,” Messi said. ”He told us what he wanted and we’ve adapted. We’re strong defensively and we have players whose quality can decide games. It isn’t very different to what we were doing before.” Perhaps not very, but it is different. And that may be part of it: Ter Stegen suggests it has helped that Valverde came with a different perspective: the former Athletic Bilbao coach was used to playing against Barcelona, analysing and identifying their strengths and weaknesses through another prism.

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When Valverde arrived, some said Neymar’s departure represented an opportunity. No one seriously thought they were better off without the Brazilian, but the coach has applied that idea. It gave him a certain margin – few demanded excellence immediately, satisfied instead with stability – and it allowed him to tilt the balance back towards the midfield, where he has added an extra man, usually playing 4-4-2 or 4-2-3-1, albeit the distribution is rarely symmetrical.

Slowly, his players grew into it. Despite not being a “typical” Barcelona player – or perhaps because he’s not a typical Barcelona player – Paulinho’s contribution has been significant. Busquets has grown into the season, taking control alongside Ivan Rakitic. Suárez overcame a knee injury and an extremely sluggish start and is now flying. Alba is having his best season. “Neymar is a great player but [without him] I have more space to go up the wing and, to tell the truth, that’s much better for me,” he admitted.

“Defensively we have gained a lot and the team is much more compact, more focused,” Alba added. “I think the team is very focused, doing the things the manager wants. Those wonderful years when everyone drooled over Barcelona there were lots of players who aren’t here any more and those of us who are here now are doing things as best we can. I think the fans are enjoying their team.”

Piqué’s warning now was well placed, alerting to the risks of euphoria where once he saw inferiority, perhaps aware too of the weaknesses that remain. This is not the Barcelona of nine years ago, when Iniesta’s baby boom happened; it is not the Barcelona of seven years ago either; or the Barcelona that won this competition three years ago; but nor is it the Barcelona of six months back. Top of the table, into the cup final, a double is close now and talk has turned to the treble, where before there was only trouble. Do that and Mercedes Rodríguez may have to draft in some more midwives.