Six minutes – that how’s long it took for Manchester United to breach a blue wall of Chelsea players. It was a neatly executed goal, but with a peculiar prelude. Ander Herrera handled the ball in his own half, turned, advanced and then dispatched an excellent defence-splitting pass, with much vertigo.

David Luiz, the anchor of Chelsea’s remodeled three-man rearguard, who reinvented himself as a reliable central defender under Antonio Conte, failed to anticipate Herrera’s pass. Marcus Rashford, Manchester United’s teen sensation, calmly and composedly struck the ball with a mundane finality past Asmir Begovic, who deputised for the injured Thibaut Courtois.

Old Trafford erupted and Rashford was subsequently praised, and even elevated to a demi-god status in the English game. He offered his team pace up front, a refreshing difference from the sometimes sluggish Zlatan Ibrahimovic. Up front, he played alongside Jesse Lingard, another Manchester United academy graduate, a novelty under Mourinho.

Mourinho’s masterstroke

But perhaps Herrera’s role in the goal was more interesting – the control with his hand, but also the tactical instruction that he had received from Mourinho to mark Eden Hazard from the onset. It was Mourinho’s masterstroke, part of a larger tactical masterclass from the Portuguese coach.

The Spaniard marked Hazard out of the game. Antonio Valencia and Ashley Young played as tracking wing-backs. Manchester United were sharp in their tackles – like Paul Pogba’s exemplary intervention on Diego Costa midway the first half – and clever up front.

In the midfield Marouane Fellaini jettonised his Sideshow Bob antics and instead played with his trademark bony brutishness, a full-proof manner to halt Chelsea. Manchester also offered width. It was United’s best performance of the season.

Slapdash would-be champions

The proclaimed champions-elect were discomfited. They looked rattled from the kick-off. Chelsea were slapdash, almost dazed. N’golo Kante was Conte’s sole player with an efficient first-half. Costa tried desperately with his best larger-than-life bully impression to harass the Manchester back line, his duel with Marcus Rojo bordering on the melodramatic at times. Hazard was – emblematic for his team – nowhere; Herrera a vintage man-marker.

Mourinho beamed at his team’s performance. Even the Special 1-1 could smile. In the second half, Chelsea were as acquiescent and concessive. Kante completed the malaise after the restart as he dallied in possession with Young teeing up Herrera, the most unlikeliest of penalty-box encroachers, whose deflected attempt looped past Begovic.

It was perhaps the first time that Herrera had ventured further than a half yard from Hazard’s side, and the Spaniard turned from provider to scorer. Where was Eden?

Not long after Mourinho decided to park the bus, he brought on Michael Carrick for Jesse Lingard, who’d played a valiant match up front. But the momentum remained with the hosts. Rashford darted across the field and his finishing was Ronaldo-esque. The youngster was electric. First, he side-netted from the right channel, then he dribbled past, and outmuscled both Luiz and Kante inside the left-channel of the box.

With just over 20 minutes left, Conte reacted. Chelsea changed their shape, with Hazard going up top alongside Costa, with Pedro and substitute Willian posted on the wings. They remained careless and indecisive in possession, in particular in the final third. Chelsea didn’t muster a single attempt on target. Conte and co were impotent.

United’s striker conundrum

In the 81th minute, Zlatan replaced Rashford. The towering Swede gallantly applauded the MVP. The No 9 offered little and it poses an interesting conundrum, even a luxury problem, for Mourinho in the future: stick with Ibrahimovic, whose many goals have often been instrumental for United, or go for a more fluid and quicker front two/three?

Zlatan as the sole focal point of the team has left United too dependent on the Swede, and without much speed in the final third. Understudy Rashford offers just that injection of pace.

For Conte, the implications of the 2-0 defeat are far graver: is his 3-4-3 formation on the wane? No longer can Chelsea enjoy their droll stroll to the glory. Tottenham Hotspur trail by just four points. Next week’s FA Cup semi-final may be the harbinger for an unexpected, protected title race. United’s win as plucky underdog was thoroughly deserved, but what’s more – Chelsea were found out.