Football is a holistic game. Advance a player here and you must retreat a player there. Give one player more attacking responsibility and you must give another increased defensive duties. As three at the back has become outmoded as a balanced or attacking formation – though not as a defensive formation – by the boom in lone-striker systems, coaches have had to address the problem of how to incorporate attacking full-backs without the loss of defensive cover.

For clubs who use inverted wingers, as Barcelona do, the issue is particularly significant. For them, the attacking full-back provides not merely auxiliary attacking width but is the basic source of width as the wide forwards turn infield. The absence of an Argentinian Dani Alves figure in part explains why Lionel Messi has been less successful at national level than at club level. For Barcelona, as he turns inside off the right flank, Alves streaks outside him, and the opposing full-back cannot simply step inside and force Messi to try to use his weaker right foot. Do that, and Messi nudges it on to Alves. So the full-back tries to cover both options, and Messi then has time and space to inflict damage with his left foot.

It is the same if Pedro plays on the right flank, and the same when David Villa plays on the left. Barcelona's wide forwards are always looking to cut inside to exploit the space available on the diagonal, and that is facilitated if they have overlapping full-backs. Traditionally, if one full-back pushed forwards the other would sit, shuffling across to leave what was effectively a back three.

Barcelona, though, often have both full-backs pushed high, a risky strategy necessitated by how frequently they come up against sides who sit deep against them. With width on both sides they can switch the play quickly from one flank to the other, and turn even a massed defence. They still, though, need cover in case the opponent breaks, and so Sergio Busquets sits in, becoming in effect a third centre-back.

That, of course, is not especially new. Most sides who have used a diamond in midfield have done something similar. At Shakhtar Donetsk, before they switched to a 4-2-3-1, Dario Srna and Razvan Rat were liberated by Mariusz Lewandowski dropping very deep in midfield. At Chelsea, Luiz Felipe Scolari would often, when sketching out his team shape, include Mikel John Obi as a third centre-back. And Barcelona themselves had Yaya Touré dropping back to play as a centre-back on their run to the Champions League trophy in 2008-09.

What is different is the degree. It is not just Barcelona. I first became aware of the trend watching Mexico play England in a pre-World Cup friendly. Trying to note down the Mexican formation, I had them as four at the back, then three, then four, then three, and I realised it was neither and both, switching from 4-3-3 to 3-4-3, as it did during the World Cup.

Ricardo Osorio and Francisco Rodríguez sat deep as the two centre-backs, with Rafael Márquez operating almost as an old-fashioned (by which I mean pre-second world war) centre-half just in front of them. Paul Aguilar and Carlos Salcido were attacking full-backs, so the defence was effectively split into two lines, a two and a three. Efraín Juárez and Gerardo Torrado sat in central midfield, behind a front three of Giovani dos Santos, Guillermo Franco and Carlos Vela. The most accurate way of denoting the formation, in fact, would be 2-3-2-3: the shape, in other words, was the W-W with which Vittorio Pozzo's Italy won the World Cup in 1934 and 1938.

Of the same species as Pozzo

Pozzo first latched on to football while studying the manufacture of wool in Bradford in the first decade of the last century. He would travel all around Yorkshire and Lancashire watching games, eventually becoming a fan of Manchester United and, in particular, their fabled half-back line of Dick Duckworth, Charlie Roberts and Alec Bell. All centre-halves, he thought, should be like Roberts, capable of long, sweeping passes out to the wings. It was a belief he held fundamental and led to his decision, having been reappointed manager of the Italy national team in 1924, immediately to drop Fulvio Bernardini, an idol of the Roman crowds, because he was a 'carrier' rather than a 'dispatcher'.

As a result, Pozzo abhorred the W-M formation that his friend Herbert Chapman, the manager of Arsenal, developed after the change in the offside law in 1925, in which the centre-half – in Arsenal's case Herbie Roberts – became a stopper, an 'overcoat' for the opposing centre-forward. He did, though, recognise that in the new reality the centre-half had to take on some defensive responsibilities.

Pozzo found the perfect player for the role in Luisito Monti. He had played for Argentina in the 1930 World Cup but, after joining Juventus in 1931, became one of the oriundi – those South American players who, thanks to Italian heritage, qualified to play for their adopted country. Already 30 when he signed, Monti was overweight and, even after a month of solitary training, was not quick. He was, though, fit and became known as Doble ancho (Double wide) for his capacity to cover the ground.

Monti became a centro mediano (halfway house) – not quite Charlie Roberts but not Herbie Roberts either. He would drop when the other team had possession and mark the opposing centre-forward, but would advance and become an attacking fulcrum when his side had the ball. Although he was not a third back, he played deeper than a traditional centre-half and so the two inside-forwards retreated to support the wing-halves. Italy's shape became a 2-3-2-3, the W-W. At the time it seemed, as the journalist Mario Zappa put it in La Gazzetta della Sport, "a model of play that is the synthesis of the best elements of all the most admired systems", something borne out by Italy's success.

Footfalls echo in the memory

To acknowledge that modern football's shape at times resembles the 1930s, though, is not to repeat Qohelet, the author of Ecclesiastes, and lament the futility of a world without novelty: "What has been will be again, what has been done will be done again; there is nothing new under the sun. Is there anything of which one can say, 'Look! This is something new'? It was here already, long ago; it was here before our time." Nor is it to argue that tactics are somehow cyclical, as many bewilderingly do.

Rather it is to acknowledge that fragments and echoes of the past still flicker, reinvented and reinterpreted for the modern age. Like Mexico, Barcelona's shape, at least when they use only one midfield holder, seems to ape that of Pozzo's Italy. Those who defend three at the back argue that, to prevent the side having two spare men when facing a single-striker system, one of the centre-backs can step into midfield, to which the response is few defenders are good enough technically to do that, and why not just field an additional midfielder anyway? What Barcelona and Mexico have done is approach the problem the opposite way round, using a holding midfielder as an additional centre-back rather than a centre-back as an additional midfielder.

But the style of football is very different. It is not just that modern football is far quicker than that of the 30s. Barcelona press relentlessly when out of possession, a means of defending that was not developed until a quarter of a century after Pozzo's second World Cup. In the opening 20 minutes at the Emirates last season when Barcelona overwhelmed Arsenal, the major difference between the sides lay not in technique but in the discipline of their pressing.

Inverted wingers, similarly, would have been alien to Pozzo: Enrique Guaita and Raimundo Orsi started wide and stayed wide, looking to reach the byline and sling crosses in. Angelo Schiavio was a fixed point as a centre-forward – no dropping deep or pulling wide for him. The two wing-halves, Attilio Ferraris and Luigi Bertolini, would have been too concerned with negating the opposing inside-forwards to press forward and overlap.

Nonetheless, the advantages of the W-W for a side that want to retain possession, the interlocking triangles offering simple passing options, remain the same. Having Busquets, the modern-day Monti, drop between Carles Puyol and Gerard Piqué is not just a defensive move; it also makes it easier for Barcelona to build from the back. Against a 4-4-2 or a 4-2-3-1, Busquets can be picked up by a deeper-lying centre-forward or the central player in the trident, which can interrupt Barcelona's rhythm (just as sides realised after Kevin Keegan had deployed Antoine Sibierski to do the job, that – counterintuitively – Chelsea could be upset by marking Claude Makélelé); pull Busquets deeper, though, and he has more space to initiate attacks.

There is a wider point here, which relates to notation. Looking at reports from the early 70s, it seems bizarre to modern eyes that teams were still listed as though they played a 2-3-5, which had been dead for the best part of 70 years. Yet that, presumably, was still how journalists and their readers thought. Future generations may equally look at our way of recording formations and wonder how we ever thought it logical that a team playing "a back four" could feature fewer defensive players than a team playing "a back three".

We understand that full-backs attack and that in a back four the two centre-backs will almost invariably play deeper than their full-backs, but the formation as we note it does not record that. Barcelona tend to play a 4-1-2-3 or a 4-2-1-3, according to our system of notation; heat maps of average position, though, show it as a 2-3-2-3. Barcelona, like Mexico, play a W-W, but not as Pozzo knew it.