After Liverpool last played, Jurgen Klopp illustrated how irreplaceable Roberto Firmino is. He cited Gini Wijnaldum’s reaction after he had to deputise for the Brazilian away at Barcelona last season, the gasping Dutchman turning to the injured forward afterwards to ask: “What the heck are you doing in that position?! It’s unbelievable! It’s so intense!”

Wijnaldum is no one’s idea of a like-for-like replacement for Firmino. Neither, though, is anyone else. Examine Liverpool’s squad and four others could play as the central attacker: Mohamed Salah, Sadio Mane, Divock Origi and Rhian Brewster. None could be called a doppelganger. In the recent history, there were two more potential No. 9s, Daniel Sturridge and Christian Benteke, who were not as much equivalents of Firmino as antitheses of him.

And then there was Wijnaldum, an attacking midfielder by trade for PSV Eindhoven and Newcastle, reinvented in a deeper role by Klopp and rebranded as a false nine in the Nou Camp. It highlighted the question of what Firmino actually is. A striker? Brendan Rodgers did not think so. A goalscorer? Yes, but Salah and Mane found the net more last season and may well do so again. A false nine? Perhaps, but not in the way Lionel Messi was for Pep Guardiola’s Barcelona, arriving late in the box but with a team built to make him more prolific. The first line of the defence? Definitely, but he is much more than that.

No tag truly fits, but in a sense Firmino is less a No.9 than a No. 10. Not by the number on his back, which suggests Firmino is the successor to Ian Rush, Robbie Fowler and Fernando Torres. Or in his status as the central attacker. But it is worth remembering that Klopp has inverted the normal forward line: the middle of the trio is often the deepest while the wingers surge past him into scoring positions. His 4-3-3 is rarely described as 4-3-1-2, but it could be; Firmino serves as the support act to Salah and Mane from behind them.

Firmino feels the opposite of the classic No. 10. Dennis Bergkamp, Gianfranco Zola and Eric Cantona might not represent a kindred spirit. He is not ostensibly as creative: after all, three team-mates recorded more assists last season, so he is scarcely the creator-in-chief. Someone with the physicality to exhaust a player with Wijnaldum’s running power is scarcely the pure technician, the specialist inventor, the antidote to football’s emphasis on running. But he is found in the same part of the pitch, a man who flourishes between the lines.

And yet if he is unique, there is the sense that Firmino fits into a Liverpool tradition. Arguably, Anfield’s last bona fide No. 10 was Kenny Dalglish. In the subsequent three decades, most of their peers have employed a fantasista. Liverpool rarely have. Jari Litmanen was a classical No. 10 who only got a handful of games, Steven Gerrard a converted midfielder who saw himself more as Bryan Robson than Cantona, Luis Garcia occupied a variety of positions, Philippe Coutinho rarely played as a 10, Yossi Benayoun, Harry Kewell, Joe Cole and Vladimir Smicer, with varying degrees of success, often played wider and Andriy Voronin was hopeless. Often strike partnerships have rendered the No. 10 redundant.

Yet Liverpool’s most successful operators ‘in the hole’, as it used to be described when the English game searched for a term for a position that other countries celebrated in the vocabulary, have tended to ally technical skills with physicality. In Gerrard’s case, it was an explosiveness that meant he could look a force of nature. In a sense, perhaps Firmino’s spiritual ancestor was a man who unites Liverpool and Saturday’s opponents, Newcastle: Peter Beardsley was an inveterate scamper, forever scurrying in the manner of a man who thought it was a sin to stand still. Much like Firmino, it is easy to imagine him winning the bleep test.

Beardsley operated in his era’s framework of 4-4-1-1 or 4-4-2. He could play the defence-splitting pass. Yet he often did so in an unfussy manner. He had a deft touch, but few frills. He did not have the spurious trickery of the self-styled entertainer. He was the workaholic in the fantasista’s spot.

The same could be said of Firmino. He has his famous no-look pass. There was an outrageous flick and trick to fool Arsenal’s Dani Ceballos last month. But by and large, there are fewer frills and flourishes. When he pierces a defence, it is sometimes with the shortest of passes: think of the ball that brought Salah’s spot kick against Arsenal, travelling only a few yards before David Luiz tugged the Egyptian back.

He is a fulcrum, but not a playmaker, whereas the typical enganche, the trequartista is associated more with a passing range and a more sedate style of play. Few countries are more associated with the No. 10 than Firmino’s homeland but he is hardly the heir to Rivaldo and Ronaldinho, Kaka and Rai.

Yet if he is an anomaly, Firmino is also the sign of the times. The classic No. 10 is an endangered species near the top of the Premier League. Now the No. 10s instead tend to be found either further down in the division, in the cases of Gylfi Sigurdsson and Manuel Lanzini, on the bench, where Mesut Ozil and Juan Mata often reside, or in other positions, like Christian Eriksen and David Silva.

A move towards 4-3-3, particularly from Klopp and Guardiola, is one reason: they field formations without a No. 10. But if Firmino feels an extreme case, there is the phenomenon that the hardest-working individual can be found in a place where some used to field a luxury player.

They are not direct comparisons, and not just because the Manchester United man is still awaiting his first league goal of 2019, but Jesse Lingard and Dele Alli are other examples of the physical No. 10, men who do not top the charts for chance creation but who bring running power to a role where vision used to be valued most.

Perhaps the 1990s represented the golden age of the pure No. 10. Particularly in Serie A, the division of responsibilities was more pronounced. Defenders defended, strikers struck and No. 10s were spared of defensive duties and liberated to create. It was an era when Italy alone had so many No. 10s – Roberto Baggio, Roberto Mancini, Alessandro del Piero, Francesco Totti, Zola – that Serie A could export Zola and Bergkamp to England.

Yet now Firmino is spearheading the trend towards universality. He is ballwinner, runner, scorer and supplier, the man who knits play together and unites Salah and Mane in appreciation of him. He is forever harrying defenders while Liverpool’s full-backs chip in with more assists than him. He is not a No. 10 in the way some of the purists would recognise, not the protected perfectionist, but the all-action all-rounder who threatens the old-style specialist.