Did Alex Ferguson have a “philosophy”? Perhaps, over the 39 years between him taking his first job at East Stirlingshire and him retiring in 2013, it is possible to pick out some essential principles, but fundamentally he changed according to circumstance. He did not formulate and then enact some grand theory of how football should be played; his greatest assets were his capacity to organise, to motivate and to evolve.

Yet recently, the assumption has been that managers must be philosophers: Pep Guardiola with his juego de posición, Jürgen Klopp and the German school of Gegenpressing, all the various followers of Vítor Frade and his theories of tactical periodisation. Since Ferguson’s final success in 2013, the only Premier League title not won by a philosopher-manager is Leicester’s in 2016 – and even they had a clearly defined way of playing.

That’s one of the reasons there has been such scepticism about Ole Gunnar Solskjær, who has no apparent philosophy beyond asking what Sir Alex would have done. But then, not having a philosophy, paradoxically, is the United way. When Noel Cantwell arrived at Old Trafford in 1960, he was appalled by how primitive the thinking at the club was. He had come from West Ham, where players would meet after training at an Italian cafe near Upton Park to discuss the latest trends and innovations. At United, training was a few weights, a few sprints, a bit of head tennis and an often violent kickabout on the cinder-strewn waste ground between the back of the stand and the railway fence.

Matt Busby spoke of his club’s pattern but as other managers – Harry Potts at Burnley, Bill Nicholson at Tottenham, Alf Ramsey at Ipswich, Don Revie at Leeds, Bill Shankly at Liverpool – began to see what could be achieved by a properly organised approach, by what was known at the time as “system football”, Cantwell was scathing about Busby’s attitude: “Give it to a red shirt? You don’t need a manager for that. How do you find a red shirt if you haven’t worked on it and talked about it?”

Yet United went on to win two league titles in that decade and, in 1968, the European Cup.

Busby’s pattern, it turned out, was good enough when you had, in Bobby Charlton, Denis Law and George Best, three of the greatest players in the world. But what’s striking is what happened next. As Charlton aged, Law struggled with a knee injury and Best’s demons overwhelmed him, there was nothing to fall back on.

Busby retired in 1969 and everything rapidly fell apart. United were relegated in 1974, didn’t win another trophy until 1977 and didn’t win the league again until 1993. Without a guiding philosophy, United drifted. They are the most successful club in England with 20 league titles, but those successes have come under three managers: they, more than any other super‑club, seem reliant on having a great leader.

By contrast, Liverpool, United’s FA Cup opponents on Sunday, are the most philosophy-driven club in England. Kenny Dalglish, Joe Fagan and Bob Paisley all developed the principles laid down by Shankly, but the boot room ensured a basic theory of play endured. Earlier than most, Liverpool went to a back four and through the 1970s and 80s they dominated English and European football by pushing high, pressing and retaining possession.

Jürgen Klopp reacts during Liverpool's 1-0 home defeat by Burnley
Jürgen Klopp reacts during Liverpool’s 1-0 home defeat by Burnley. His side are struggling to adapt to the bizarre circumstances of this season. Photograph: Paul Greenwood/BPI/Shutterstock

What went wrong in the early 90s can be debated. The legacy of Hillsborough, clearly, took an awful toll and perhaps Graeme Souness was not the right choice to ensure continuity, but there were also seismic changes to the environment, in how the game was played and in its economics. The coming of the Premier League and satellite television opened up financial opportunities United proved far more adept at exploiting, while the introduction of the back-pass law made it harder to retain possession. Having a philosophy that had yielded almost constant success for years arguably hampered attempts to adjust to a changing world.

Three decades on, this season is being shaped by similar impulses.

Liverpool have the philosophy. Klopp stands at the forefront of the pre-eminent German model of the press. His style can even, just about, be seen as a modern development of the classic Liverpool style.

United, abroad in the wilderness that follows the retirement of a great manager, have ricocheted through disparate approaches, from old‑school British under David Moyes to possession-heavy Van Gaalism to José Mourinho’s low‑block periodisation to Solskjær’s Fergie revivalism.

Only over the past year or so has their squad begun to look even vaguely coherent, but they are still reliant on individuals. Bruno Fernandes has been exceptional since arriving from Sporting Lisbon at the end of last January, but the flipside of his 19 goals and 14 assists in 32 Premier League starts is that if he isn’t firing, United often aren’t creating. Paul Pogba, Edinson Cavani and Marcus Rashford have produced flashes of genius, but while United are undeniably dangerous on the counter, the major doubt that remains over Solskjær is his capacity to formulate coherent attacking plans.

That was Liverpool’s great strength, pressing with intelligence and rigour and then, having won the ball back, having the organisation to take rapid advantage. That their front three are struggling – one goal in the past four games they have played together – is indicative not only of a dip in form on the part of Mohamed Salah, Roberto Firmino and Sadio Mané, but also of changes to the midfield forced by injuries at centre-back.

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There is a curious sense that in the present bizarre circumstances, as the relentlessness of the schedule diminishes planning and recovery time and makes injuries more likely, the interconnectedness of Liverpool, usually such a strength, has made it harder to adapt.

At United, a club unwedded to a philosophy, the emphasis is far more on individuals and moments. The structures are less complex, the more traditional qualities of motivation and unity more important. That is contrary to the direction of most modern tactical thought, but this season it may prove an advantage.