everal epochs ago, back in the long-forgotten wilderness of October 2020, a good deal of airtime and column inches were expended on the curious deluge of high-scoring thrillers that had occurred in the first few rounds of the new Premier League season. Aston Villa put seven past Liverpool. Leicester put five past Manchester City. José Mourinho’s Tottenham, who pretty much everyone agreed were a team going places, put six past Ole Gunnar Solskjær’s Manchester United, who pretty much everyone agreed were sinking without trace. Everywhere you looked, defences were on fire. By the end of the fourth round of fixtures, the average number of goals per game was a scarcely credible 3.79. As ever, football’s content-industrial complex kicked into gear. Various airy theories were propounded. The lack of crowds. The truncated pre-season. The new handball laws. Dodgy keepers. In a newspaper column, the former England striker Stan Collymore declared that “the art of defending is dead”, a pronouncement he had previously made in both 2016 and 2014. At which point, something entirely expected happened. The goals started to dry up, and to an extent that suggested this was something more than the usual reversion to the mean. Since early October, just 2.48 goals per game have been scored in the Premier League, a rate consistent with its lowest-scoring seasons ever. In games between the traditional Big Six, that drops to 1.92. This season is on course to be the first since 2014-15 to fall short of a thousand goals. In short, far from ushering in a new golden age of emaciated attacking football, it turns out that the early fiesta of autumn goals provoked a fierce corrective impulse. Coaches realised that in this bedraggled, unstable season, the first team that could get a grip of its defence would enjoy a disproportionate competitive advantage. And perhaps, therefore, it is no surprise that the two clubs who retooled themselves most effectively on that front may well end up carving up all four major trophies between them. Manchester City’s defensive transformation since a crushing 2-0 defeat at Spurs in late autumn has been well documented. In many ways, it is a process that hit its apex against Paris Saint-Germain on Tuesday night, as a side feted for its abundance of attacking riches and a coach derided for asking “what is tackles?” repelled the world’s most expensive front line in the most time-honoured way imaginable. There were towering headers, salty grapples, epic slides, any number of heroic, last-ditch, potentially anatomy-reconfiguring blocks. Between them, City’s defence has now faced Kylian Mbappé, Neymar and Erling Haaland for a combined total of almost 500 minutes. Those minutes have produced a grand total of three shots on target, and no goals. The shift has been one of attitude as much as tactics. Stylistically, Pep Guardiola’s side are largely a similar animal to the one that started the season. What has changed is the seriousness and rigour, a change that largely aligns with the arrival of the ashen-faced Rúben Dias from Benfica: the sort of defender who seems to take no real pleasure in football and therefore sees no reason why anyone else should either. “I was never a person that loved to just enjoy life,” he said in a recent interview. Understand: it’s not like he wants to put his face in the path of a speeding football. It’s just that he’s considered all the alternatives, and they’re even worse. Chelsea’s metamorphosis, by contrast, has been undertaken largely on the hoof. Such was the haste with which Thomas Tuchel was installed as Frank Lampard’s replacement in January that he was forced to formulate his tactics for his first game against Wolves on the plane from Paris to London. This was where he settled upon the compressed five-man defence that has led them to an improbable record of 18 clean sheets in 24 games. Tuchel’s defensive system bears similarities with the 3-4-2-1 adopted by Antonio Conte in the title-winning season of 2016-17: attacking wing-backs pushed high up the pitch, a double-locked midfield to squeeze out counterattacks. Above all, individuals have also stepped up: Antonio Rüdiger, Andreas Christensen, the masterful and weirdly underrated César Azpilicueta. Should we mention the money? City and Chelsea fans get needlessly prickly when you do so, but equally it feels bizarre to overlook the lavish bankrolling both clubs have enjoyed over the last decade. The crux of this issue is not simply the investment itself – which can always be sliced and diced to prove whatever point you want to make – but the stability and leeway it affords you. City can calmly stride into the market and sign six of the 11 most expensive defenders in history (plus a £40m Nathan Aké as insurance) in the knowledge that should any of them not work out, a replacement can simply be plucked out of thin air. Chelsea also spent big on Ben Chilwell in the summer, but perhaps their greatest asset has been the luxury of choice. Eight defenders have played 10 or more games for them this season. In more straitened circumstances, and certainly in the midst of a pandemic, there would surely be greater pressure to cash in, to slim down, to sell. Instead, the likes of Marcos Alonso, Kurt Zouma and Emerson can simply be kept on as fringe players, injury contingencies, fresh legs in a tiring season. The real question here is whether the pivot to defence is a temporary contingency, or a portent of a wider shift. The Premier League is not alone in seeing a drop in goals: the Bundesliga and La Liga have also registered small declines this season. This year’s Champions League knockout stages have seen just 2.71 goals per game, compared with 3.39, 3.14, 3.28 and 3.52 in the previous four seasons. Perhaps European football at its elite end is moving into a new age of austerity, in which the recent vogue for exuberant attacking chaos evolves into a more restrained, structured game. If so, then it is currently these two clubs, with their plush squads and shrewd coaches, who look best placed to adapt.