The first part of Ernesto Valverde’s plan for Wembley lasted under an hour. The idea was to rest Lionel Messi and Sergio Busquets, ready for Wednesday’s game with Tottenham, but Barcelona were losing 1-0 to Athletic Bilbao on Saturday, so he decided it was time to bring them on.

Messi made an equaliser for Munir El Haddadi and hit the post but it was not enough. Barcelona were held again: defeated in midweek by bottom-placed Leganés, held by Girona before that, they had dropped seven points in six days.

“I knew we were taking a risk leaving out Messi,” Valverde said. Hindsight can be cruel but even before it had seemed likely the logical conclusion of leaving Messi out might be putting Messi back in again.

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The reliance on him is considerable, Busquets admitting: “It’s not Messi-dependence, it’s being intelligent and making the most of the best player in the world: when I have the ball, I try to look for him – sometimes excessively.”

Making changes that restore the strongest XI is a recurring theme this season, not just with Barcelona’s captain.

At Real Sociedad, Phillipe Coutinho and Busquets started on the bench; with Barcelona trailing 1-0, both were introduced before the hour. Against Girona, 2-1 down after 51 minutes, Coutinho and Ivan Rakitic were reintroduced seven minutes later. At Leganés, where they trailed 2-1, Luis Suárez and Jordi Alba, rested to start with, were returned to the team on 61 and 70 minutes respectively. Alba and Suárez were two of the four players who had played every minute until then; Messi was one of the others, which is why he began on the bench against Athletic three days later.

It did not work. At Real Sociedad, Barcelona scored twice to win the match but against Girona they only managed to equalise and the same thing happened against Athletic. The change had come too late, as well as deepening the sense of distrust in those who had started. At Leganés, they did not even get the draw: with more than half an hour to turn it around, Barça created a single chance and barely even rebelled. Two draws and a defeat in three games leave them seven points worse off than at this stage last season. It also leaves them top, somehow. “Leaders, despite everything,” ran Sport.

“Everything” is not so far off.

“This might sound opportunistic but is there a problem with Barcelona’s strength in depth? Can you rotate as you would like? Only when you do, it seems it does not work,” Valverde was asked after the Leganés loss. “You’re right,” he replied, “itis opportunistic.” When Busquets was asked about rotation a few minutes later, he responded: “Next question.” But it was asked again three days later. “We can’t just rely on Messi to solve things; if we’re here it’s because we have ability and did big things at other clubs,” Suárez said. “We have enough not to depend on one player,” Messi said.

Facebook Twitter Pinterest Barcelona players train at Wembley before the group game against Tottenham. Photograph: Glyn Kirk/AFP/Getty Images

There is a reason why Barcelona are keen to rotate and why Messi was rested. Last season, Barcelona won the double, not losing a league game until the penultimate weekend with the title already won. In Europe, though, they were defeated in Rome, caught unawares, outrun and eliminated.

Suárez admitted he felt “regret” at having played 90 minutes against Leganés three days before the Roma defeat, and this time they were determined not to fall into the same trap. A double winning season ended up feeling like a disappointment; this time, the preference for the Champions League was been expressed publicly – “that lovely cup,” Messi called it – which at some subconscious level may also have played a part in their domestic difficulties and which made rotation non-negotiable, an eye always on Europe.

But it is not just Messi and it is not just the rotations either, not just a failing of the reserves. Not least because they have not exactly been overwhelmed with opportunity: Arturo Vidal has started only twice, Arthur once, and Suárez was right: there should be sufficient talent to win without Messi, however dominant his presence, however easy it is to cede responsibility.

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The only player to have played every minute is Gerard Piqué and right now fans would be pressed to find a worse performer, directly at fault for goals in each of the last three matches.

This is systemic, too. Barcelona have been flat, fragile and disjointed, easily opened up. After the Athletic draw, Suárez suggested their attitude had not been good either. They have trailed in six of nine games. It is not so much that they are conceding lots of chances as clear ones; without pressure on the ball, finding the space beyond them has been remarkably simple.

“It can’t be that we concede every game,” Messi lamented. “We have to be stronger defensively. We come off a year when it was very hard to score against us.” This year they have conceded as many league goals after seven games as they did in the first 18 then. It may be that at Wembley – a stadium of immense significance for Barcelona – they return to the 4-4-2 they played last season, losing Ousmane Dembélé from the front three.

Yet in Europe, Barcelona’s problems go back further. The last time they won away was a year ago, and that was thanks to an own goal from Sporting’s Sebastián Coates; they have won just three of 10 on the road; Suárez has not scored away since Rome 2016, 13 matches ago. Messi has scored 20 times against English clubs – home and away against Arsenal, City and Chelsea, in two finals against Manchester United – but has got only one in their past five away trips in the knockout stages: against Chelsea last year. Now he returns to London, and to the stadium where he led Barcelona to the title in 2011.

That feels a long time ago, so does Berlin 2015. Those past five results on the road help to explain it and make startling reading: defeated 2-0 at Atlético, 3-0 at Juventus and 4-0 at PSG, Barcelona drew 1-1 at Chelsea, rather fortunately. Then last season, they went to Rome, having won the first leg 4-1. Everyone thought the treble was on. Instead, they were defeated 3-0 and eliminated, full of regret. Lessons were learned, or so they hoped. One solution was supposed to be rotation but that is proving a problem too.

Like others before him, this weekend Messi was taken out, then hurriedly put back in. Against Spurs, he will start: at least that part of the plan still stands.