Such is the attacking intent of Liverpool and Manchester City that rarely could games between the two be defined as an immovable object meeting an irresistible force. 

This afternoon's crunch game at Anfield might just provide some thunder and lightning, however. Much depends on the champions' three musketeers – Mo Salah, Sadio Mane and Roberto Firmino – remembering their swords and being fully fit, something that hasn't always been the case this season. That's the irresistible force taken care of, perhaps of greater intrigue is the immovable object; otherwise known as City's iron-clad defence.

Certainly, defensive solidity or, indeed, a lack of it has characterised the two foes this season.

It has been a tale of four central defenders: partners who have built a two-man fortress in front of the Manchester City goal and a pair who have been missing for Liverpool due to season-ending injuries. Further evidence of Liverpool's woes in that position was confirmed in midweek when Joel Matip, who has deputised for the errant Virgil Van Dijk and Joe Gomez, was also ruled out for the rest of the campaign with ankle ligament damage.

In a season when goals have been down on previous campaigns – there were 613 scored at this stage last year compared to 593 this time around – shutting opponents out has never been more important. City, so often mocked for spending the GDP of a small African country (or rich Emirati state) on their backline, have finally found the secret formula in Ruben Dias and John Stones. They have not lost with Stones in their starting line-up this season and since the pair franked their partnership at the heart of City's defence at the end of November, Pep Guardiola's side have conceded just once.

Stones' revival has gone from clapped-out jalopy to sports-car status in a matter of months. He may have scored three goals in his last seven appearances but it is the attribute that he has been scrutinised for most – his defending – that he has elevated to another level.

He has benefited, undoubtedly, from the arrival of the rock-solid Dias. The duo make the perfect complement as a centre-back pairing and the rugged Portuguese is a frontrunner for the player of the year award given the transformative effect he has had. In many ways, it is reminiscent of the manner in which Virgil Van Dijk took Liverpool to the next level.

During the recent cat-and-mouse chases between the two clubs over the past couple of seasons as they have vied for Premier League supremacy, each team has produced goals in industrial quantities.

Liverpool rattled in 258 in the three seasons prior to this one at an average of 2.2 per game while City have been even more prolific, scoring 303 in the same timeframe for an average of 2.66 per match. This year, there has been a tail off, however, with City at 1.85 and Liverpool at 1.95. But because City have excelled at the back, conceding at a rate of one goal every 150 minutes, they have surged ahead at the top while Liverpool, never watertight even in full flow, have dropped 26 points so far, as opposed to 15 for the entirety of the previous campaign.

One the one hand, Guardiola has demonstrated a capacity for adaptation that had often seemed beyond him. His idealism has been tempered by the absence of a consistent presence in attack, a long-term injury to Kevin de Bruyne and the emergence of Dias, who has made the most clearances of any City player this season and the second most interceptions, as his minister for defence.

On the other hand, Liverpool's defensive problems have had a less obvious, but materially significant, impact on their attack. With Fabinho and Jordan Henderson often asked to fill in at centre-back Liverpool have been denuded of their two most important central midfielders. Henderson's pressing was a key feature of their title win and it was no surprise that – when he was reinstated to his natural berth for the second-half in the 3-1 victory at Tottenham recently – Liverpool were at once their snarling selves, producing one of their best performances of the season. But, too often this time around, that intensity has been missing from Jurgen Klopp's team. 

Meanwhile, the protection Fabinho usually offers to the two men behind him is less secure and so the effect of losing two players has been more akin to losing four. Of course, Liverpool have known this since Van Dijk and Gomez were crocked. Yet instead of acting quickly – presumably because they were top of the table heading into January – they gambled, waiting until news of Matip's injury forced their hand. The addition of reinforcements became inevitable but whether the arrival of Ozan Kabak on loan from Schalke 04 or Preston's Ben Davies are the answer is another matter.

The former was part of a defence that shipped 49 goals in the Bundesliga this season and his parent club lies adrift at the bottom of the Bundesliga. There are question marks over his mobility and reaction times. Davies, meanwhile, was regarded as one of the best defenders in the Championship, but so too was Joe Rodon when Spurs plucked him from Swansea City and, while the Wales international has shown flashes of how good he could be there have been teething troubles along the way. No two players are the same, of course, but Davies is 25, has no pedigree at the top level and interest in signing him appeared to extend to Celtic and a handful of other Championship clubs before Liverpool moved in.

At a combined outlay of around £2.6m for Kabak and Davies, it seems negligent of Liverpool to have waited so long to address the gaping chasm in their backline. Their decline in form over January shines an even brighter spotlight this afternoon on what has become the biggest fixture in the English calendar. When the sides met in November 2019 at Anfield, it was billed as an early title decider with Klopp's side opening up a nine-point gap on Guardiola's following a 3-1 win. A victory for City, who have a game in hand on the champions, this time around would almost certainly end Liverpool's defence of their title.