As open as Jurgen Klopp is, and as enthusiastically as he will talk about the principles of his football idea, there is one area the German remains completely guarded on. That is about the specifics of Liverpool’s supreme pressing: how it is co-ordinated, how it is drilled.
“Klopp won’t let anyone watch the sessions,” one source close to the club says. This may, in quite a literal sense, be the secret to success at the very top end of the game.
A huge improvement in pressing is widely seen by figures around Bayern Munich as the major reason the German club won the Champions League. A drastic drop-off is meanwhile viewed as one of the major reasons that Manchester City again failed in the competition.
Pep Guardiola is all the more relevant to this because pressing has evolved several times over since his 2008 re-interpretation of the approach totally revolutionised football. It has become more focused, more specific and more co-ordinated, with its effect enhanced by wider improvements in sports science and fitness. This has in turn contributed to its use. The game is much more athletic than it was even a decade ago. More players can run faster for longer. You only have to look at the endurance of "full-backs" like Trent Alexander-Arnold, and the number of wide players in the list of fastest sprinters from Uefa’s technical report for last season.
You might also notice the number of German or German-based players there, from Leipzig’s Lukas Klostermann to Chelsea’s Timo Werner.
That does not feel a coincidence, since the area has really become the preserve of pressing. It is where coaches pore over its principles most, and where most of its innovations and evolutions have come from. That can be seen in the impact a figure like Ralph Hasenhuttl has had at Southampton, and the influence on the Championship of managers like Thomas Frank and Gerhard Struber. One prominent figure in Spanish football last week lamented to The Independent how stale Real Madrid and Barcelona look in contrast.
Many in Germany credit one man with much of this. They call it the Ralph Rangnick revolution, for the way he put the idea in place at Hoffenheim, and then developed it at Leipzig. Klopp has credited a 4-1 Borussia Dortmund defeat to Hoffenheim in 2009 as an epiphany moment for his own view on pressing.
The effects of all this - and Julian Nagelsmann’s own interpretation - will be encountered by Manchester United this week. It is going to be an instructive challenge for Ole Gunnar Solskjaer to solve.
Alex Zorniger directly worked under Rangnick at Leipzig as one of their first managers, and explains the principles of the approach now, and its more modern interpretations.
“Against the ball, players need to know what it means for their space when an opposition player is in a specific position - like if one striker appears in one area. So, in a 4-3-1-2, you try to close the wings, so they have to pass into the centre where you have the majority of your players.
“It is like the pieces of a really good watch. Everything has to fit. Everyone has to know their function. That needs to be trained.”
This is where the trade secrets come in, and where the sophistication of any specific approach can have a superior effect.
It can be seen in the near uniqueness of Liverpool’s approach, and how the full-backs are essentially attacking players, while the only true “defensive” players are the centre-halves and two number-eights.
It can be seen in the utter assurance Bayern had in playing so high last season, and how infrequently they were caught out. It should be no surprise the assistant responsible for this, Danny Rohl, previously worked at Leipzig.
“Bayern’s work in chasing the ball, and the organisation, was on a completely different level to before,” Zorniger argues. “Completely.”
While the technical and tactical coaching is the foundation, Zorniger says the real difference comes in the psychological coaching.
“In training, you try and stress the players as much as possible, so that actual matches feel slower. Then it’s much easier to do anything and make decisions. It’s like Pavlov’s dog. In the perfect situation, pressing is second nature, and everything works like an orchestra.”
It is for this reason that one Premier League coach - who has been viewed as one of the high priests of pressing - sees the discussion as much more holistic, and feels you can’t quite isolate pressing in that way.
“It is about player commitment, and the outlook you create in the squad,” the figure, speaking off the record, says. “Any approach is subject to the willingness of the players.”
This is something that Zorniger agrees with, and says it is why Leipzig have specifically gone for players under a certain age, and with relatively limited experience.
“Their mental hard disk is kind of empty, and the intensity they can play at is higher. You can implement the principles much faster.
“The more experienced players, they know there are a number of options. They’ve often played in a number of systems. Football players in general don’t want to look like fools, and playing high or running high can create a lot of risk. They might look at easier solutions, like dropping behind the ball.”
Fundamentally, this kind of modern pressing involves an intensity of work that the most indulged senior players might now feel they are beyond. There are many stories of how Neymar was completely resistant to any kind of drills at Paris Saint-Germain, although Thomas Tuchel is said to have recently done a better job of coaxing him around.
Some of this rationale might also help explain bigger theories about football, like how sustainable a manager’s approach is.
While there are now arguments within the game that Guardiola’s idea of defensive pressing is no longer at the top level, it’s also possible that it’s just difficult for players to be put in as much after four years of the Catalan’s unique intensity; that they need a mental break.
Zorniger points to similar with Germany 2018, who many felt were too sated by victory
“They had bad organisation when they lost the ball, and bad responses afterwards. That is a question of mentality.”
The approach requires the highest commitment, which is why it currently represents the highest level of the game. The circumstances, however, may also distort the future of it.
In the short term, the Covid-congested calendar means coaches won’t have the same time to work on these systems. Such pressing may temporarily become the victim of its own intensity.
Bayern manager Hansi Flick had exactly this thought when watching Liverpool lost 7-2 to Aston Villa. “This is what happens when the press doesn’t fire,” he remarked to a colleague. That intensity requires such a level of integration, and to be so finely tuned, that the drop-off can be stark when even one component is missing. A hole in one area will create a chain reaction.
The same happens if any single player doesn’t buy in. The system breaks down. It doesn't go like clockwork. This is sometimes why managers appear to inexplicably drop some individuals.
It also reflects Zorniger’s point about players not wanting to look like fools. That cuts to the debate Roy Keane and Klopp had about “sloppiness”. A collective’s risk can bring individual mistakes, and the two can be confused.
The situation therefore may bring some surprise results.
In the long term, then, some in Germany have been worried that the focus on pressing has increasingly led to a reductiveness in the country’s youth production.
Sven Mislintat has been complaining that the academies are now just producing a series of energetic pressing drones, rather than difference-making players. Matches where it’s just pressing systems crashing against each other, with no discernible differences in individual quality, aren't too hard to imagine.
That in itself reflects the evolution and next step of a cycle Guardiola touched upon at the end of his own playing career in the mid-2000s. The Catalan found that his technical game was being overrun by tenacity.
“I haven’t changed,” Guardiola argued. “My skills haven’t declined. It’s just that football now is different. It’s played at a higher pace and it’s a lot more physical. The tactics are different now, you have to be ball-winner, a tackler, like Patrick Vieira or Edgar Davids… players like me have become extinct.”
It sounds familiar. It’s also why Jack Grealish is so distinctive a player, because he has that rare ability to beat the press and escape with a dribble in quite an old-fashioned way.
That’s the thing about any given tactical trend. It will provoke unexpected responses, that prompt further evolution.
For the moment, the reality seems clear.
“The way top teams handle their defensive organisation to win the ball back has been decisive in every major title for the past few years,” Zorniger argues. “Even France looked for organisation in transition. I deeply believe that a team that is 100% perfect playing with the ball will lose to a team that is 100% perfect organised against the ball.”
The latter is what Klopp so works on. We have seen the effects on the pitch. It’s why he won’t let anyone see the work behind it on the training pitch.
It is tantamount to one of the game’s decisive trade secrets.