‘One lie, repeated many times.” That was José Mourinho’s mantra before his Manchester United team had even kicked a ball in the Premier League, when responding to questions about the lack of academy players he had trusted over the years. Surely now he has a golden opportunity to end such talk – one of the main concerns before he was appointed – that his approach to management is at odds with a club where youth promotion and success have lived symbiotically for many years?

Marcus Rashford, the precocious talent who few had heard of this time last year, has given him that opportunity. Another game, another fearless display from the 18-year-old, this time at Hull City, on an evening where he not only scored the winning goal but also provided the kind of zest and attacking vivacity that the game, and United’s play, desperately needed.

It was not the first time either. Rashford has continually done so since making his surprise debut in the Europa League last season, coming in at short notice when Anthony Martial pulled up in the pre‑match warm-up to score twice against Midtjylland.

He did so again in the Manchester derby. He did so against West Ham United in the FA Cup. He did so on his England debut against Australia and he did so in Lens at the European Championship, when Roy Hodgson’s side were struggling to break down Wales.

In many ways it is remarkable that United’s fans had to wait 251 minutes of the league season before seeing him in action. They were not to be disappointed when they did, Rashford producing a cameo performance that increased the pressure on a tiring Hull before providing the decisive impact in injury time.

Mourinho calls him “the kid”, a moniker that once befell a certain Spanish striker before his move to Liverpool, and Rashford became the first teenager to score under the Portuguese coach in the Premier League. The next youngest was Arjen Robben during their Chelsea days, who was only a few months shy of his 21st birthday.

It is becoming difficult to make an argument for Rashford’s exclusion from the starting XI against Manchester City after the international break, should all Mourinho’s players return to Carrington fully fit. From thereon in, he has to be an integral part of United’s plans rather than a bit-part player handed 20-minute bursts here and there.

Rashford’s displays have been too consistent to suggest that he is riding the crest of a wave. Every time he plays, he makes an impact. Before he scored the winner at Hull he had already forced an excellent save from Eldin Jakupovic and delivered an inviting ball across goal that only just evaded Zlatan Ibrahimovic.

He has the deadly combination of pace, skill and composure and, although Hull’s caretaker manager Mike Phelan said afterwards that his appearance off the bench reminded him of one of Ole Gunnar Solskjaer’s great cameos with United, such a role seems unlikely in the long-term.

Asked if Rashford was better utilised as a late substitute rather than a starter, Mourinho said: “I think top players are better on the pitch than on the bench. But coming against a tired team that was trying to hold off high-intensity waves of attacking football, for sure he comes fresh and comes sharp and he causes them problems. But I think top players have to have more time on the pitch than on the bench. I just want to say that he’s a very good player and a very good boy. He has the perfect head for an 18-year-old: very stable, not in the moon, so I think he has everything. He’s going to play a lot of matches.”

Rashford will soon join the England Under-21 squad – which Mourinho believes will benefit the player more than a senior call-up – and the dilemma the United manager could have is how the youngster slots into his starting team. Ibrahimovic’s place is a given, meaning Rooney, an out-of-form Martial and Juan Mata come under scrutiny.

Phelan, a man who has seen many United players progress from youth to first team, described Rashford as an “exceptional talent”, while Rooney said the teenager is “one of the brightest talents in Europe”.

He is arguably the most positive thing to emerge from the Louis van Gaal era at Old Trafford and, for Mourinho, represents a ready-made opportunity to place his faith in youth. Unlike with previous players at former clubs, there is little risk in playing Rashford. No transition period from under-age football to the highest level is required.

Mourinho can forget colour-coded lists and youngsters who played 10 minutes for him once upon a time. Rashford is ready to make more of an impression than any of those before him.