Sometimes, the easy explanation tells the whole story. Or near enough, anyway. Why Liverpool’s crown as reigning Premier League champion has slipped before the first blooms of spring is no great mystery. There is little need to sift through performances, searching for some failure of character or imagination or ability, to understand how it came to this.

Virgil van Dijk tore a knee ligament on October 17, in the early minutes of the Merseyside derby. Not quite four weeks later, on November 11, his regular defensive partner Joe Gomez blew out a tendon while away on international duty with England. And that, to a large extent, was that. Liverpool’s aspirations, at that point, had to be downgraded.

Soccer has a dispiriting tendency to scorn mitigating circumstances — in the lexicon of sports, explanation is too often seen as a synonym of excuse — as Roy Keane, the hard-boiled former Manchester United captain, rather neatly encapsulated in the aftermath of Liverpool’s humiliation by Manchester City on Sunday. “They’ve been bad champions,” Keane said. To be a “big club,” he said, is to cope with whatever setbacks are thrown your way.

There is truth in that, but it carries with it an air of brutal, gleeful oversimplification. Liverpool cannot, of course, escape blame for the collapse of its title defense. The club chose not to add a central defender to its squad last summer, recruiting instead a reserve left back who made his first and only Premier League appearance in the dying minutes on Sunday. That seemed a risk even without the benefit of hindsight.

At the same time, Jürgen Klopp, the club’s manager, has cut an increasingly waspish figure as the season has unfurled. He also must shoulder some responsibility, though. He has leaned too heavily on a handful of players, rather than sharing the burden more evenly. Even he has admitted that his squad is as mentally and physically drained as it looks.

More important, Klopp has overseen a team that has become grinding and predictable, reliant on the methods that brought a Champions League triumph in 2019 and the Premier League last year, even as Liverpool’s high-energy, high-intensity press has tuned down and his raiding fullbacks have found their edge dulled.

Liverpool’s opponents have learned — both Burnley and Brighton have won at Anfield in recent weeks, shutting down the champion using essentially the same playbook — but Klopp’s team has not, the manager apparently insistent on doing the same things over and over again in the desperate, vain hope that the outcome might be different next time.

And yet all of that is inseparable from the fact that Liverpool has been playing for months without its first-choice central defense, and that its first reserve, Joel Matip, managed to start only nine Premier League games before his season, too, was ended by injury.

To cope, Klopp has deconstructed his midfield, drafting first Fabinho and then Jordan Henderson into the back line. The team has lost its rhythm. A swarm of other injuries — Thiago Alcantara and Alex Oxlade-Chamberlain missing the first third of the season, Diogo Jota and Naby Keita the middle third, the usual wear-and-tear of a long, hard campaign — has left him with little choice but to play those members of his squad who were left standing.

In those circumstances, trying to inculcate a new style of play is hardly realistic. Liverpool does need to evolve; with its resources, it should not be in a position where it is fretting about whether it can fend off West Ham, Everton and, possibly most pertinently, a surging Chelsea to finish in the top four. But in terms of retaining the title, it did not so much meet a setback as run into a roadblock.

There is a useful contrast, here, with its most recent conqueror and its heir apparent. So entwined have been the fortunes of Liverpool and Manchester City over the last three years that there is now a temptation to see them as being somehow inextricably linked, the success of one taken as a direct indictment of the other’s failure.

This season only seems to reinforce the parallel. Liverpool’s struggles this year do not perfectly match those City faced in the last one: Where City was volatile, scoring great rafts of goals only to freeze completely every few weeks, Liverpool’s fade has been a slow-burn demise, set in motion even before the title was won, the team sputtering through the autumn and only stalling completely at Christmas.

But at first glance, the cause and the effect are the same: the lack of defensive cover, the oxygen debt to be paid after two seasons at the most rarefied heights, the sense of a wall being hit, all of it coalescing as Manchester City ran rampant at Anfield on Sunday, the pendulum swinging irrevocably back toward Pep Guardiola’s team.

There is an easy explanation for that, too. Last summer, Guardiola and his employers knew their team needed more steel. City had lost nine games the previous season, its efforts to win a third straight title undone not only by Liverpool’s relentlessness but by its own glass jaw.

So as much of European soccer fretted about the economic impact of the coronavirus and the subsequent shutdown, Manchester City went and spent $140 million on two defenders: Ruben Días and Nathan Aké. And that, to a large extent, was that. Días has, in the months since, emerged as the cornerstone on which Guardiola has built a new, parsimonious, indomitable version of City, one that is now set to reclaim the championship.

In this case, though, the easy explanation only scratches the surface. Guardiola has not simply slotted a new central defender into his team and pressed play. He has, instead, retuned his approach. His team has been a touch less expansive, a touch more controlled, built on a more conservative midfield. He has overseen this shift in the space of a few months, on the back of a summer in which he did not have a preseason, during a campaign in which there is scarcely any time for training.

Partly, Guardiola has hinted, he took that risk — and it was, ultimately, a risk — to suit the realities of this most congested season. But partly, too, it was driven by the same impulse that made him recruit Días and Aké: an awareness that City needed to evolve once more if it was to outwit opponents who knew what to expect.

What has enabled him to do that is the one element that has eluded Klopp. City has not been free of injury this season — Sergio Agüero has barely played, and both Gabriel Jesus and Kevin de Bruyne have missed considerable stretches — but its burden has been undeniably lighter than Liverpool’s.

Nine of Klopp’s players have started 17 of Liverpool’s 23 Premier League games. Nine have already racked up 1,500 minutes in the league. At City, by contrast, only four players have reached those figures. Or, to put it another way, 13 of Guardiola’s players have started 10 games or more.

It is to his credit that he has rotated that heavily. Guardiola has more readily understood the contingencies of this season than almost all of his peers; he spoke, around Christmas, of urging his team to run less, not more, in the early weeks of the campaign.

But it does not immediately follow that it is to Klopp’s detriment that he has not had the same realization, that he has not altered Liverpool’s approach sufficiently to enable his players to cope with the test in front of them. It may be tempting to see Liverpool and City as counterweights — the rise of one a comment on the fall of the other — but the circumstances and the contexts are different. Klopp might have followed Guardiola’s lead, had he had the opportunity. Or not. It is impossible to know. Sometimes the easy explanation tells the whole story. And sometimes it does not.