Around the turn of the year, when five of the major European clubs were looking for new managerial candidates, one official involved in elite-level recruitment let out a sigh. “There is nothing in football as difficult as choosing a coach,” came the complaint.

The frustration was from the fact that there are so many variables, especially when a manager moves from one financial tier to another. They might have the right style but not the right personality. They might fit the tactics but not the culture.

Although clubs are trying to add some science to this, feeding details through algorithms, there’s still a huge element of human trial and error. You can’t always account for how a manager’s approach translates to a different dressing room.

Liverpool host tonight’s Champions League game at Anfield with a twist in that sense, given the Bayer Leverkusen manager, Xabi Alonso, could indeed have been in the home dressing room, in place of Arne Slot.

Given those challenges in selecting a manager, it is striking how perfect Alonso seemed for Anfield. The Basque had of course played at the stadium, as a hugely admired midfielder who was key to Liverpool’s 2005 Champions League win. That ensured he had the experience and personality to handle big stages, which has lent itself to a persuasive managerial charisma.

At the root of this is a hugely sophisticated tactical ideology, one that Alonso’s personality helps apply. It was only more attractive that the approach has elements of Jurgen Klopp’s game, with all of this contributing to the historic achievement in breaking Bayern Munich’s hold on German football by winning the domestic double unbeaten.

There are further echoes of Klopp in such managerial alchemy. Alonso simply seemed perfect.

And yet, it’s difficult to believe that even someone so ideal as the Basque could have done as well as Slot. The Dutch manager’s start is as close to perfect as you can get in terms of results. It’s been remarkable.

While many might reasonably say the fixture list has been kind, affording Slot a soft landing, Liverpool have responded well to increasingly harder tests. There was the late equaliser against Arsenal and then the comeback against a fine Brighton, as Liverpool added intensity to their control.

These are the two sides of the form they’re on now. While it’s fair to say we won’t see the “real” Liverpool until they have a properly tough run of games, it’s just as fair to say this isn’t yet a real Slot team. These are only the early days of a completely new tactical approach for the squad, where it feels like the main imprint so far has been a broader control of possession. What is it going to look like when Slot has the team fully in tune, or even all the players he wants?

These are exciting times for the club, and play into an enticing game at Anfield.

Leverkusen’s more ingrained approach can test where Liverpool are now, as the German side seek to end Slot’s 100 per cent record in the Champions League so far. Alonso’s team themselves have two wins and a draw from their three games. Both teams can go some way to ensuring a place in the automatic qualification places of the top eight.

Given that aim still seems so opaque, with this week’s games only seeing the group stage hit the halfway point, Liverpool and Leverkusen’s clash is another of those fixtures where it reflects wider themes.

There's the bigger question of whether one of these managers can go to a higher level, to that Klopp-Pep Guardiola standard of achievement.

A significant reason that coaches have been so difficult to appoint is that we are now moving into a new era, defined by a new generation.

It was in 2016 that the Premier League proclaimed itself the league of star managers, after the appointments of Guardiola, Jose Mourinho and Antonio Conte complemented the work of Klopp and Mauricio Pochettino. Thomas Tuchel was rising in Germany, Carlo Ancelotti and Luis Enrique pre-eminent in Italy and Spain, respectively.

Now, Tuchel and Pochettino have taken themselves to international management, and it feels like they would be only considered by major clubs as short-term appointments. Those same clubs no longer consider Conte due to the baggage, a factor having long tainted Mourinho.

Klopp arguably succeeded the Portuguese as Guardiola’s main rival at the peak of all this, only to take himself out of management altogether. Everyone is meanwhile waiting for Guardiola’s next move, which is anticipated to be at international level, while Ancelotti will eventually step down at Real Madrid – potentially for Alonso.

That has left all of the major clubs looking at what comes next, with none of the candidates having the CVs to make them guarantees. There feels much more of an unknown to the new generation, which is arguably exciting in a different way.

It’s also what makes Alonso’s decisions all the more interesting, as well as being indicative of the state of play.

A big question will be why he isn’t actually managing Liverpool on Tuesday. Alonso's obvious charm will only give that more of an edge, especially with how Slot’s low-intensity public persona is the one element that has been raised as a potential detraction. He's no Klopp... or Alonso.

The truth is that those at Liverpool were playing down the possibility of appointing their former midfielder quite early on. They were looking around for other candidates, but there was also an awareness Alonso was likely to stay at Leverkusen.

That is admirable in the modern game, where the inclination is constantly to jump ship because you might miss your chance. Instead, Alonso felt the obligation to give Leverkusen more, and certainly the chance at a Champions League.

Slot, for his part, similarly refused earlier offers because he wanted to give Feyenoord the maximum. Tottenham were rebuffed, prior to Ange Postecoglou’s appointment in May 2023, with the Dutchman only moving when the time and job were right.

It is possibly a lesson for this generation, who ironically have more choices in a situation where clubs have fewer guarantees.

Manchester United’s appointment of Ruben Amorim, who takes on Manchester City in Lisbon on Tuesday in one of his final Sporting matches, is all the more interesting in that context.

There is also another choice relevant here, one that will frame how the Anfield game will be played. Slot is of the Guardiola school. Alonso is from the school that has deviated from it.

This match isn’t just a sliding doors moment, then. It potentially opens the door to a new era. A new generation is ready to take its place.