Manchester United 3 Arsenal 2 comment: Teenage rampage exposes Arsenal's frailties

What must Danny Welbeck have thought? This was the future that was supposed to be his

Manchester United's 18-year-old striker Marcus Rashford scored twice (Getty Images)

“Unbelievable,” said Michael Carrick. He was talking of Marcus Rashford. Who else? The sentiment was shared around Old Trafford. The Stretford End rose en masse to applaud him from the pitch at the end of a stirring victory for Manchester United. The man-of-the-match champagne would follow to mark one of the most remarkable league debuts seen at this epic theatre.

Don’t get carried away, I hear you say. It might already be too late. Graeme Souness had United storming back into the top four on the back of an 18-year-old boy playing his first Premier League game. Perhaps he is right. Rashford scored with his first shot, and added a second three minutes later. And this after galvanising the midweek turnaround against FC Midtjylland in the Europa League.

“It is just crazy. I can’t explain it,” said Rashford, struggling to piece together the significance of the four days that have transformed his life. Arsène Wenger admitted knowing nothing of Rashford before his Thursday night introduction. He is intimate with him now. And how the introduction hurt.

What must Danny Welbeck have thought, looking at young Rashford in the tunnel? This was the future that was supposed to be his; the solution, according to Sir Alex Ferguson, to the striking demands at United and England. The dual skinning of Hector Bellerin and Gabriel in the 15th minute was a beautiful, expressive hors d’oeuvre. Fourteen minutes later he was in the right place at the right time.

This does not happen by accident. Rather Rashford, at 18, displays all the predatory instincts of a natural-born No 9, or in his case 39, intuiting space in the box and striking through the ball unerringly. Here, Welbeck was cast in the same role he occupied at Old Trafford, stuck out wide and asked to do the fetching and carrying. When he had a sniff between the posts from a free-kick, he skilfully directed an acute header past David de Gea.

What a day for Fletcher Moss Rangers FC, the local football club that unearthed both Rashford and Welbeck. And what a day for Louis van Gaal, who – with this victory and his comic act of simulation in the technical area, emulating the going to ground of Alexis Sanchez – might just have extended his time in office.

This was only his second trip inside the pitchside white lines since his arrival. It brought the house down and set forth a blizzard of Twitter memes. United’s difficulty has been one of personnel in a period of change, and ultimately a lack of leadership on the pitch, in the dugout, and in the boardroom. The Van Gaal regime had seemingly run its course and then, when he thought it couldn’t get any worse after Anthony Martial limped out of Thursday’s warm-up, along came fate with its gift of Rashford.

Van Gaal has not been helped by an appalling run of injuries, to which Marcos Rojo contributed early in the second half. This has forced constant shuffling of the back four and compromise elsewhere. Of course, the world receives only mixed messages about his future, the latest coming via his outrage at the Jose Mourinho question given vent in the Dutch media.

This is the way to answer your critics, by imbuing United with a sense of adventure and urgency. The team pulled this off with only 39 per cent possession, which is its own commentary on Van Gaal’s stubborn attachment to possession-based fundamentals. Alongside Rashford, Guillermo Varela and second-half substitute Timothy Fosu-Mensah were also full of running. When Memphis Depay learns to direct his effort in the requisite manner, United might do with even less of the ball.

Depay was again full of tricks but not with any clear idea of what the result might be. Until he learns to adapt his penchant for rolling the sole of his boot over the ball to greater purpose, he will largely remain on the edge of things rather than at the heart, where his ability has the potential to place him.

Arsenal managed to lose to a team with Carrick at centre- half, which condemned them out of hand. They dominated the ball but not the shape of the game. This was never a test of Arsenal’s footballing credentials but of character, belief, and how they see themselves. With their history, resources, geography, Arsenal ought to have the hauteur to take on any, but seem further away than ever.

Critics talk of the step Manchester City are required to make when Arsenal are no further forward in their development as a global team. In that they betray their traditions and possibilities as a club housed in one of the world’s great cities, contesting one of the great leagues.

Arsenal did half a job in the Champions League on Tuesday before losing their shape and conceding mental ground, allowing the idea of Barcelona as a great club to weigh too heavily in the balance. United didn’t scare them. Nor should they have. But to what end are Arsenal aiming if they cannot get past a makeshift and inexperienced United side?

“Is this the Emirates?” sang the travelling support as Arsenal took an increasing hold before Rashford went to work. Put that ditty away boys until you can sing it with menaces. Arsenal might be seven points clear of United but, with the North London derby to come, what price this being a turning point for both clubs?