* It was back in April 2014 when Jose Mourinho engineered the most decisive moment in a Premier League title battle he was essentially no part of. Liverpool hosted Chelsea at a raucous Anfield in a game practically treated as the Reds’ coronation; Mourinho took absolute delight in tripping them up just short of the finish line.

Manchester City would go on to lift that crown, and whether or not Tottenham can play that role as they look to usurp Chelsea remains to be seen. But Mourinho must again be praised for ensuring things remain interesting at the summit, regardless of whether he is playing one of the main roles. With six games remaining, Chelsea have a four-point gap to defend, and they look more vulnerable than ever.

* It seemed that Mourinho had spent much of his Friday afternoon digging himself a hole. “When it is still mathematically possible to finish in the top four I think if we play against Chelsea with our second team you would kill me,” he said. “The football country would kill me.”

By Sunday afternoon, Mourinho was standing over said hole, pointing a loaded gun at his own temple. Few could have foreseen a starting line-up free of Zlatan Ibrahimovic, captained by Ashley Young in a forward position, for a crucial April fixture against Chelsea.

The only surprise is that we were all surprised. The manager’s constant complaints over the schedule his side been subject to throughout the season due to their cup exploits, coupled with a finely-balanced Europa League quarter-final second leg in midweek, meant that naming a weakened side was a no-lose scenario. If Chelsea emerged victorious then Mourinho’s hands had been tied by the authorities; there was nothing he could do. Draw or win, and he had masterminded a win over the champions-elect with an XI nowhere close to full strength; there is nothing he can’t do.

* The expectation was that this would be a tense, cagey, nervous affair, with one team more interested in avoiding defeat than winning, and the other feeling the pressure of a title race that shows no sign of slowing down.

The reality was that United enjoyed a wonderful start and Chelsea looked eerily leggy; only one of these sides looked as though they had played in midweek, and it was not the one sporting red.

But United will have known the importance of capitalising on their early superiority. They had won just six Premier League games of 16 at Old Trafford this season before Sunday, constantly failing to exploit their dominance. Marcus Rashford’s seventh-minute strike, the forward played in by a beautiful Ander Herrera through ball, was United’s first goal in the opening 20 minutes of a home game this campaign. Chelsea did not look back in October when Pedro scored within a minute; United knew not to here.

* Gary Neville praised Herrera for “breaking up play” in the build-up to Rashford’s goal, the Sky Sports co-commentator hailing the United midfielder for his basketball skills.

The debate will rage on as to whether the goal should have been ruled out after Nemanja Matic’s pass hit Herrera’s hand before the Spaniard released Rashford, but it is a pointless argument. Chelsea were misplacing passes, tripping over each other and committing foul throws before and after the goal; this simply accelerated the inevitable breakthrough. Conte will know better than to blame a questionable referee decision for his players’ error-strewn performance.

* It was after the previous meeting between these two sides that Antonio Conte complained that Eden Hazard “couldn’t play football”. It was less a hilariously bizarre and childish attack on one of the Premier League’s finest footballers, more a pointed remark regarding the opposition’s tactics.

Chelsea won that game 1-0, N’Golo Kante’s strike handing them a place in the FA Cup semi-finals, but discussion after the game surrounded Hazard. The Belgian had been targeted throughout, and was fouled six times by Mourinho’s band of hitmen, yet was still the game’s best and most influential player.

Hazard was again the subject of Mourinho’s carefully concocted Eden project, but there was no systematic team fouling this time. Instead, Ander Herrera was awarded the honour of shadowing Hazard throughout, and he did a bloody good job. The Chelsea winger failed to register a single shot or complete a dribble. Zlatan Ibrahimovic has been United’s best player this season, but chief b*stard Herrera runs him a close second.

* Chelsea’s preparation for the game was hindered by two injuries to first teamers. Thibaut Courtois was reported to be unlikely to start as early as Sunday morning, the goalkeeper having suffered an injury in midweek. Marcos Alonso was named in the starting line-up, but was withdrawn after feeling unwell in the warm-up.

A simple show of hands would tell you that Courtois is the most important of the two, but Chelsea missed Alonso far more than their fallen keeper here. In a Venn diagram of Hazard’s struggles, the left circle would be marked ‘Ander Herrera’, and the right title ‘An off day’. The middle section can be dedicated to Alonso, whose significance in Chelsea’s season has been overlooked, but was evident at Old Trafford.

The Spaniard offers much-needed width and forward running, as well as necessary cover and overlapping runs for Hazard. Cesar Azpilicueta is the better defender, but Alonso’s all-round game is superior. Chelsea might well have struggled without him, but his absence on the left-hand side was sorely felt. Of the Blues’s five Premier League defeats this season, it is no coincidence that he has started just two. He is not Chelsea’s best player – he is not even their best defender – but few are a better fit in Conte’s system.

* Midway through the first half, and the visitors were starting to find something approaching their groove. Mourinho has made a number of pointed remarks regarding his former side’s counter-attacking tendencies this season, and Victor Moses led the charge this time.

With Marouane Fellaini otherwise indisposed and Herrera starving Hazard of oxygen, the final member of United’s midfield three was charged with putting out the fire. Paul Pogba did so with aplomb, and was quietly impressive throughout. The Frenchman attempted 61 passes, 47 of which came in the opposition half – both the highest in the game. The understated nature of his showing will not appease the critics, but Pogba can live safe in the knowledge that a haircut and a couple of emojis will be permitted by the footballing gods this weekend.

* Forty-six minutes had passed when Diego Costa called a brief truce with Marcos Rojo in order to do something no Chelsea player had done in the entirety of the first half. His stoppage-time effort which flew past the post in frustration was the visiting side’s first shot of the afternoon.

When Costa is firing, there are few better in the Premier League. But when he is handled as well as he was by Rojo and Eric Bailly here, he offers absolutely nothing. He was dispossessed 22 times in total – more than any other player – and conceded the most fouls (5). The Spaniard hardly had the greatest supply from a listless midfield, but he won no headers and won the ball from just five of his 23 duels. He has also now failed to score or assist a goal in ten of his 15 matches this calendar year. Michy Batshuayi must be wondering quite what he’s done wrong.

* When discussing Rashford – as we most certainly will later – it is difficult at times to remember that this is not a seasoned professional at his peak, but a young player learning the trade. The same stands for Eric Bailly. This was Rashford’s 61st senior game at the age of 19; it was the 82nd of Bailly’s career at the age of 23.

Mourinho spoke of Bailly carrying “the question mark of someone who has never played at such a big club with so many responsibilities and so many expectations” when he made him his first signing at United manager in the summer. The central defender is excellent on the ball, tall, fast, strong and more tactically astute than many give him credit for, but evolving from a Villarreal rookie into a valued United squad member was a thankless task.

Alongside the ever-improving Rojo, Bailly prevented Chelsea from registering a single shot on target, and rendered two of the league’s finest forwards utterly obsolete. United’s second-youngest starter was excellent.

* Four minutes into the second half, and the game was practically over. Chelsea were on the ropes in the first half, saved only by the salvation of the bell. That it was Herrera’s final blow that knocked them out of the Old Trafford ring was almost fitting.

The Spaniard spent the first half shackling Hazard, taking a brief respite to thread a sumptuous assist into Rashford for the opener. His goal had more than a touch of fortune about it, rebounding in off Kurt Zouma’s ankle and over Asmir Begovic’s head, but it was just reward for a workmanlike performance. Quite how he managed to manoeuvre himself for the shot while Hazard was still in his pocket, only he will know.

It is clear to see why Herrera is a fan favourite at United. He is the embodiment of his manager: A sh*thouse with the talent to change any game, and an individual fans of his club love, and opponents love to hate.

* While Herrera is excelling in Mourinho’s class, one of United’s model pupils over the ages was impressive. The unexpected captain led by example.

Ashley Young was unfortunate not to have claimed an assist in the first half when Rashford could not quite connect with his driven cross, but the 31-year-old did manage to make his most telling contribution in the second, robbing Kante of possession before bursting into the area and laying the ball off for Herrera to finish.

Be it by Sir Alex Ferguson, David Moyes, Louis van Gaal or Mourinho, and as a right-back, left-back, winger or striker, Young has been a prominent member of United’s squads down the years. This proud club has not seen a more accomplished captain since the days of Fellaini.

* Conte’s response came soon after, with Cesc Fabregas called upon from the bench. Moses, with his sum total of one tackle, one interception and a 50% pass-completion rate, was the sacrificial lamb.

The Chelsea manager has managed to cover up his Achilles heel this season with the padding and protection of a wonderful debut season in the Premier League, but Mourinho exposed it at Old Trafford. When the Blues needed a game-changing substitution, the boss was found wanting.

The first-half performance called for a half-time change, but Fabregas was introduced at 2-0 as Conte tried to stick a plaster over a gun-shot wound. Willian followed after the hour mark, and Ruben Loftus-Cheek came on with seven minutes remaining. None of the three substitutes attempted a shot, created a chance or completed a dribble.

Conte is the only Premier League manager to have used all of his substitutes in every game, but all too often he leaves it all too late. Seventy of his 96 substitutions this season have come in or after the 75th minute; four have come before the hour mark, only one of which has come at half-time. Loftus-Cheek has not been handed more than eight minutes in a single Premier League game this season.

* With ten minutes remaining, United delivered the final blow. Their top goalscorer rose from his seat on the bench, ready to take to the field. Old Trafford erupted in appreciation.

The plaudits would generally be reserved for Zlatan Ibrahimovic, who was sent on by Mourinho for a quick run-out before the Europa League action in midweek. But the fan adulation was surely for Rashford, the game’s best player.

It was a delight to watch the 19-year-old lead the line, an opportunity he has barely been handed this season. He took it with both hands, tormenting a Chelsea defence that has made a habit of dominating strikers. He bullied Cahill, Luiz and Zouma with his strength, and embarrassed them with his pace. It was a quite stunning performance.

* Mourinho deserves utmost credit for his handling of Rashford, of course. The fear was that England’s Bright Young Thing would have his light dimmed by the Portuguese, such is his hatred for young players. If anything, the United boss has assisted in his development more than any other manager could.

Would Rashford have liked to play as a central striker more often this season? Most certainly, but his time spent on the wing has proved invaluable in his progress. He naturally drifts when playing as a striker anyway, and that tendency was vital to United’s game plan. His six crosses were at least three more than any other player.

For all the talk of Rashford (19) being wasted as a winger, it has proved invaluable in his development. He drifts out wide as a CF anyway. pic.twitter.com/XfiTV7wHiv — Football365 (@F365) April 16, 2017

Rashford is destined to be part of United’s attack for years to come; he is absolutely good enough now, and will only improve. What’s more, he has already endured a terrible run of form, only to emerge stronger: After no goals in 20 Premier League games, he has now scored in his last two. His manager’s faith through the September-April drought should not go unnoticed.

* For much of this season, Mourinho has felt like an old dog incapable of performing his old tricks, never mind learning new ones. The Portuguese has preached the power of the club’s unbeaten run for months, but United still sat sixth heading into this game.

The manager’s tactics in matches against United’s direct rivals had been particularly uninspiring. The club’s only Premier League victory against a fellow top-six side this season came against a Tottenham side enduring their poorest run of form in the winter. Mourinho had come up against Pep Guardiola, Jurgen Klopp and even Arsene Wenger, and failed to win the tactical battle each time.

His most ignominious and damaging loss of all came against Conte in October, but this was the perfect revenge. Mourinho’s game plan was perfect, with Herrera countering Hazard, Lingard and Rashford providing width and pace going forward, and the team working as a cohesive unit.

When Mourinho reacted to the second-half introduction of Cesc Fabregas within six minutes by replacing Lingard with Michael Carrick, the Portuguese proved that he does still have a knack for the big occasion. Carrick came on to close the midfield channels that Fabregas loves to exploit, and Conte was thwarted once more. Mourinho has long been regarded as one of the finest directors of a big game, but has relied more on individual brilliance in recent years. This time around, it was not Ronaldo’s, Hazard’s or Ibrahimovic’s, but his.

* You get the feeling that Mauricio Pochettino is relishing the role reversal. “We got the three points and now the pressure is on Chelsea to win in Old Trafford,” said the Tottenham manager on Saturday, his side having crushed Bournemouth.

This time last year, Pochettino was bemoaning a fixture list which often saw Tottenham, the chasers, play their corresponding fixture after Leicester, the leaders, who invariably won. It both increased the pressure on Spurs and reduced the margin for error.

Tottenham are still chasing this time around, but, perhaps crucially, are playing their games first. By the time Chelsea face Middlesbrough on May 8, Tottenham could be one point behind. This race is not yet run.

Matt Stead