If you boiled the Premier League down to a sticky liquor of notable body parts, a few key ingredients would probably be discernable. Sergio Aguero's right foot, for instance, or maybe David Silva's left. Xherdan Shaqiri's thighs. Andy Carroll's sledgehammer forehead. Marouane Fellaini's chest, David Luiz's locks, Mesut Ozil's eyes. Diego Costa's lunatic grin. (If you're constructing a composite humanoid in your head here, please pass on my condolences to your sleep patterns.)

Eventually, though, you'd be left with just one thing in your pan, staring plaintively up at you: Jose Mourinho's face. It is, in many ways, the true star of the English game, capable of entertaining, confounding and riling – often within the same few seconds. It makes so many back pages, major newspapers should just probably just bite the bullet and dedicate news correspondents to it full-time. If a picture is worth a thousand words, photos of Mourinho's face should, by rights, have made match reports redundant already.

Already this season, we have seen the full gamut of emotion. Initially, even as Manchester United won their first three games of the campaign, the Portuguese opted for a strict glowering-only policy, maintaining the deathly expression of a man convinced the universe would implode if he were to crack a smile. Away from the dugout, there was that viral video with John Bishop, in which Mourinho appeared to be afflicted by an outbreak of genuine joy (although, given Bishop's somewhat tenuous relationship with the concept of humour, we cannot rule out the possibility that Mourinho was simply making the most of an rare opportunity to simulate amusement).

All that, though, was just a warm-up for Sunday, when Mourinho's face lit up United's meek surrender to Chelsea. There was incredulity as Pedro tiptoed his way through the wreckage of Chris Smalling's reputation to put the hosts ahead. There was genuine anger as Eden Hazard fired wide after a short corner routine that should have been dealt with. There was the wistful regret of the homecoming-gone-wrong as Gary Cahill made it 2-0. There was, as Chelsea added a third and a fourth, begrudging acceptance. Time and again the television cameras zoomed in on his furrowed brow.

A common take on Mourinho in recent weeks is that, for all his achievements and acumen, he has begun to be bypassed by a new generation of managers. In the Premier League, the likes of Jurgen Klopp and Mauricio Pochettino are coaxing dynamic, positive performances from their teams. Further afield, young prodigies like Thomas Tuchel and Julian Nagelsmann are coming to the fore, preaching pressing, flexibility and intensity. Compared to them, the argument goes, Mourinho is wedded to the past, clinging to a scheme that no longer works at the top level.

That may be true. It may be that Mourinho, despite only being 53 – Klopp is only four years younger - has already enjoyed his salad days and is on the down slope. Time will reveal all. But for now it is worth noting that there are mitigating circumstances, the most significant of which was painfully apparent at Stamford Bridge.

United, for all the spending, all the bluster, lack the on-pitch leadership on which Mourinho's methods usually rely. For 90 minutes in west London, Mourinho was left squirming alone in the spotlight.

His tactics have varied over the years, but he has usually been able to rely on dedicated footsoldiers to translate the backs-to-the-walls spirit of his media histrionics onto the field. Think of the players who have thrived under the personality cult – think of John Terry, Didier Drogba, Frank Lampard; of Walter Samuel, Marco Materazzi, Javier Zanetti; of Jorge Costa, Vitor Baia, Ricardo Carvalho. All bought into Mourinho's vision wholeheartedly. They would have run through a wall for Mourinho without a second's thought and set the tone.

Where are those players at United? When Mourinho looks out from the technical area, does he see characters capable of embodying his own bulldog spirit (presuming that internal fire has not yet gone out)?

Wayne Rooney has clearly been an inspirational figure in the United side over the last decade and remains an influential member of the squad, but it's tough to lead the charge when you're grappling with apparently terminal career decline from the (dis)comfort of the bench or sat at home injured.

The armband, instead, was worn by Smalling at Stamford Bridge. Even discounting his wretched performance on the day, it's doubtful whether the 26-year-old has even a dash of the snarl and conviction that has characterised the best United captains of the millenium. Roy Keane, Gary Neville and Nemanja Vidic snarled, seethed, snapped into challenges and generally played football as though their lives depended on it. Smalling looks and at times defends like a Mr Potato Head toy perched atop a hat stand.

Who else? Daley Blind and Juan Mata bring intelligence and poise but are hardly going to lead a side into battle. Fellaini is far too hapless and flaky to set an example. Michael Carrick and Morgan Schneiderlin cannot get in the side. Bastian Schweinsteiger, who can boast more than a century of Germany caps and owns a World Cup winners' medal, has been jettisoned. If you are looking for experience then does it make sense to have the former Bayern captain rotting back at Carrington?

Jesse Lingard, Marcus Rashford and Anthony Martial are still wet behind the ears. Ashley Young and Antonio Valencia are quiet. Eric Bailly cannot be expected to become a pillar of leadership so soon after arriving.

There are those who contribute. David De Gea, United's best player, is a leader by example, even if his influence will always be limited by his position. Ander Herrera, while no traditional enforcer, certainly has the requisite fire in his belly and lifts the team with his energy. But neither is yet the sort of all-out talisman that Mourinho needs.

The two main options that present themselves for that role only underline the issue. Zlatan Ibrahimovic is a huge personality and his dedication should be an example to team-mates. "He brought his own physiotherapist with him. Everyone was left open-mouthed by that," Andreas Pereira swooned last month. There is little doubt that, when in form, he will exert a massive influence on the field, as he did in the opening weeks of the season.

But for all the talk of a contract extension, this is a player coming to the end of his career; a wildcard contracted for one last hurrah. He can hardly be expected to become a pillar of a Mourinho's project in the long term.

The same is not true of Paul Pogba; the Frenchman should be a fixture of this side for the next decade. But Pogba has spent the first months of his time back at Old Trafford grappling with his own role in the side and has only influenced games in brief spells. Against Chelsea, as in many games this term, he looked muted.

Mourinho's hope will be that Pogba finds his voice as he finds his form – that he justifies Marcelo Lippi's view that he is a "born leader". But the 23-year-old himself still appears to have some doubts: "I don’t know if I’m a leader like people say," he said this summer. While £89million buys plenty of talent and star power, it may not have given Mourinho a solution in the short term.

Ahead of Wednesday's League Cup game against Man City, Mourinho admitted that his life in Manchester is a "disaster". He has been living alone in the Lowry Hotel since arriving at United, with his family back in London. "We try to feel it, we try to see the evolution of our feelings and see how we cope with the situation," he sighed.

He is due some sympathy for that. But unfortunately, it's not just in his personal life that Mourinho is adrift. For with few natural leaders on the pitch, he may also feel he is flying solo at United for the timing being. Against Chelsea, the loneliness was etched on his face.