The only possible complaint that could be directed at Manchester United after this game is the question of why they have not played with this kind of authority more often this season. Oh, this was more like it from José Mourinho’s team. They have never looked so accomplished in his era and, in the process, they have opened up the title race in a way that makes it bewildering they are so far back in Chelsea’s wing-mirrors.

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Mourinho can certainly take enormous satisfaction from the way his players out‑thought, out-ran and out-fought those from Stamford Bridge, even if a man with his ambitions must also harbour a deep sense of regret that it still leaves his team 15 points back, not even guaranteed the prize of Champions League football next season. Mourinho had devised a tactical masterclass.

His players were enthusiastic students and Chelsea were rattled. How rattled? Well, it probably sums it up that N’Golo Kanté, of all people, was responsible for losing the ball before the second goal. It was, Mourinho said, a “special performance against special opponents”. Or, to use Ander Herrera’s description, “almost perfect”.

Chelsea still have a more obliging run-in than Tottenham Hotspur in second place but Conte’s men have seen a 13-point lead whittled down to four in just under a month and, if nothing else, it has applied an element of vulnerability to what was in danger of becoming a procession. Conte admitted afterwards that Spurs were now “the best team” and though it would be out of character for Chelsea to lose their nerve, perhaps United have shown the blueprint now for beating, or at least negating, the league leaders.

Mourinho cannot have found it easy to leave out Zlatan Ibrahimovic but the decision to drop his leading scorer was based on boldness rather than conservatism, and fully justified bearing in mind the chasing Marcus Rashford gave David Luiz and Gary Cahill. Rashford was exceptional but Herrera pushed him close to be recognised as the game’s outstanding performer on a day when the Spaniard was assigned an old-fashioned man-marking role on Eden Hazard. Herrera stuck to his man like a limpet but he also weighed in with the second goal as well as setting up the first for Rashford with an exquisite piece of vision.

To give Chelsea their due, Herrera also got away with an obvious handball before the opening goal, seven minutes in, but Conte did not try once to use that as an excuse for everything that followed. United’s starting XI had managed only 12 league goals all season but Mourinho had worked out everything to a T. It was his first win against Chelsea since leaving the club and though Conte still leads 2-1 on that front, it was also a reminder that opposition fans might have been a little premature this season in serenading United’s manager with chants of “you’re not special any more”.

Mourinho’s formation – a fluid 3‑1‑4‑1-1 – was certainly unorthodox but it was also designed to minimise Chelsea’s counter-attacking threat. Matteo Darmian, like Herrera, had his own specialist role, rarely leaving Pedro’s side. Ashley Young, an unusual choice for captain, seemed inspired by the role and was applauded off by his manager when he was substituted late on.

Ibrahimovic, Mourinho explained, has looked tired recently, but there was more to it than that. Mourinho not only started with Rashford but also had Jesse Lingard operating just off the striker, a decision based on the suspicion that Chelsea’s centre-backs would be vulnerable to quick, penetrative running.

That was certainly the case with the opening goal and the controversy surrounding Herrera’s handball should not entirely obscure the fact it was a beautifully weighted pass once the referee had given him the benefit of the doubt. All the same, it was easy to understand why Chelsea were aggrieved.

They had been on a promising counter-attack of their own when Herrera used his left hand to intercept Nemanja Matic’s pass. At this level it was poor from the referee, Robert Madley, to let it go, and in a matter of seconds Rashford was clear, running behind David Luiz, taking a couple of touches to steady himself and then angling his shot past Asmir Begovic.

Begovic was in goal for Chelsea because Thibaut Courtois had injured himself in a promotional basketball shoot for the NBA and as if that was not galling enough for Conte, there was more disruption in the warm-up when Marcos Alonso was forced out with a virus.

Kurt Zouma was fast-tracked into the defence, with César Azpilicueta initially switching to Alonso’s role as a left wing-back before swapping places with Victor Moses on the right. It did not work on either side.

Chelsea had lost their full-strength XI with unfortunate timing but that does not fully explain their lack of cohesion. Moses was removed eight minutes into the second half and however much of a pest Herrera was, Conte is probably entitled to think Hazard ought to be accustomed to the close attention of opposition players. As for Diego Costa, he had one of those days when he seemed to base his entire strategy on antagonising whoever was marking him. It seems like old hat now, and Mourinho’s defenders had been drilled not to react.

If anything, the ordeal could have been even worse for Chelsea bearing in mind the dangers Rashford posed his markers and the lack of activity in David de Gea’s penalty area. Four minutes into the second half, Kanté’s heavy touch from a penalty-box clearance allowed Young to dispossess him. As Young moved into the penalty area, Zouma prodded the ball away and Herrera let fly from 20 yards. The deflection off Kanté wrong-footed Begovic and Chelsea, for the first time in a long while, no longer seem immune to danger.