It was a match made in heaven. Manchester United had desperately searched for the perfect partner in the three years after Alex Ferguson ended their wonderful union. The glass slipper fit neither David Moyes nor Louis van Gaal. Jose Mourinho was supposed to be different.

This summer finally saw the Portuguese wed with the club he had lusted after for over a decade. Marcus Rashford was the page boy. Wayne Rooney was the drunk uncle whose antics had threatened to overshadow the celebrations. Paul Pogba was the lavish gift bestowed upon Mourinho by his new partner. Victory in the Community Shield consummated the marriage, but already the cracks are showing.

Against Watford, United were abysmal. It was Moyes. It was Van Gaal. It was Mourinho. Save for a brief 20-minute spell after Marcus Rashford’s equaliser, they were second-best. Watford were more aggressive, more committed, more organised. Watford were considerably better.

In previous games this season, United’s negatives could be pinpointed to one main deficiency. Whether it has been Pogba’s struggles to assert himself, the inability to find the right position for Rooney, or the defensive lapses which typified defeat in the Manchester derby, there was just one overlying problem. It is difficult to know exactly where to start with the issues which Watford exploited at Vicarage Road.

Pogba was anonymous. “It’s normal that after the first game he has a little decrease,” said Mourinho this week, defending his world-record purchase. But this is a midfielder in free-fall. The clamour has been for the manager to change his system to accommodate his expensive gift, but the Frenchman was diabolical in his favoured midfield three. He lost possession 19 times, more than any other United player, did not have a shot on target, and registered the lowest passing accuracy of any outfield player for the visitors (74.6%). The 23-year-old needs a break, but is it ever possible to drop the world’s most expensive player?

Rooney was terrible. Glenn Hoddle reserved particular praise for the captain on two occasions: When he ran the ball out of play, and when he hit a cross out for a goal kick. Both times the 30-year-old was praised for his attacking intent, but Rooney’s determination has never been in doubt. His quality, however, is undeniably on the wane. Mourinho can play him as a No 10. He can play him as a winger. He can play him as a midfielder. He can play 4-2-3-1 to accommodate him. He can play 4-3-3 to accommodate him. He cannot reverse the passage of time, something which has ravaged Rooney’s body. The mind is willing him to do things he no longer can.

Eric Bailly was exposed. The summer signing enjoyed a wonderful start to the season, but the belief has always been that this is currently a defender capable of equal measures excellence and error. He completed a solitary tackle, made two interceptions, and continued pressure from Troy Deeney eventually showed. Bailly registered a 100% passing accuracy from 22 passes in the first half; he completed just over half of his 19 passes in the second half. A poor performance reached its nadir in the final minute when his uncertainty led to Marouane Fellaini conceding a penalty. Just as United have struggled in the past three years, Bailly could barely handle two minutes of Success.

Fellaini himself was polarising. He won possession ten times more than any other United player (16), and had 88 touches and 67 passes – game-leading statistics – but he made glaring mistakes for each of the goals. Etienne Capoue and Juan Camilo Zuniga benefited from the freedom of Hertfordshire for their goals, both coming as a result of simple cutbacks – simple cutbacks into an area a defensive midfielder would surely monitor. Yet Fellaini is another United player being asked to play in a position in which he does not excel, and was almost a third – and wholly unnecessary – centre-half at times. His clumsiness in conceding the penalty was typical. One would have paid to have seen the reactions of Ander Herrera, Morgan Schneiderlin or Michael Carrick.

Even Marcus Rashford, Zlatan Ibrahimovic and, long before his removal, Anthony Martial struggled. Watford did not struggle to deal with a blunt attacking threat, and despite boasting 60% possession, United registered just two shots on target. Watford, playing with a straightforward plan, a clear identity and as a cohesive unit, tested David de Gea five times. The Spaniard failed on three occasions, and criticism will come his way for the opening goal. Said criticism will fall at his feet, of course, due to his refusal to save anything with his hands.

And yet United’s most guilty party, the one most responsible for their current malaise, is the man sent to rescue them from the reigns of terror and boredom put upon them by David Moyes and Louis van Gaal. This was Mourinho’s 14th defeat as a manager in his last 32 games, and the first time he has lost three consecutive matches in 90 minutes since he was in charge of Porto. That was 14 years ago. After his struggles at Chelsea, Mourinho’s mask slipped long ago. He is still scrambling around on the floor to find it.

Where the Portuguese was once a tactical master, he finds himself trying to fit square pegs into round holes. Where the Portuguese was once an authoritarian, he continues to cede power to his undroppable captain. Where the Portuguese once had a file of Plans A through Z, he now limits one of the most expensive sides to have ever been assembled to kicking the ball long to a 34-year-old free transfer. The buck stops with the manager – the most disappointing individual in all of this.

“I’m always concerned when we don’t get the results we need,” Mourinho said post-match, but it is not even necessarily a case of results. United have been outperformed in their last three games, two of them against sides they have no excuse not to dominate. There is not a crisis at Old Trafford, but the honeymoon is well and truly over.