The technique was strikingly similar – and equally effective – as Cristiano Ronaldo’s famous “knuckleball” free-kick technique. When Rashford scored the second goal to secure United’s 2-0 win, even the celebration – a leap into the air and a twirl – channelled the Portuguese superstar.

Rashford is starting to emulate Ronaldo in other ways, too. Just like the United legend, Rashford is now truly hitting his stride in his fourth season at Old Trafford.

The 21-year-old has three goals and an assist in four starts for Solskjaer, and has arguably been even more influential for the Norwegian than the rejuvenated French World Cup winner.

“His free-kicks, that was the start against Cardiff, and then he does it again, he’s got a great hit,” added Solskjaer, who became the first United manager since Matt Busby to win his first four games at the club.

“Tough test [playing up front on his own]. He gets kicked, and he gets tackled, he goes for headers, he wins, he challenges, he runs. He is going to be a top, top number nine, definitely.”

Ronaldo’s sudden transformation from show pony to genius was almost overnight, as if something clicked in his head, and Rashford’s potential seems to have been unlocked by Solskjaer.

The sentiment among United fans was that, under Jose Mourinho’s defensive shackles and given the Portuguese boss’ clear preference for Lukaku, the academy product’s talent was being wasted.

Jamie Carragher claimed in September Rashford might have to leave the club to become world class. Now he has seen the difference.

“That is maybe some of the early signs of the work of Solskjaer on Marcus Rashford,” said Carragher on Wednesday.

“It’s, ‘Can he finish?’ Solskjaer has told Rashford, ‘Cool, calm in front of goal’. He’s said, ‘He’s a far better player than me, but in these positions I was better than him’.

“When he’s got time to think in front of goal, like he did there, that may be your work on the training ground.”

It’s quite something when a former Liverpool player praises a United player. Less surprising was the admiration from Carragher’s Sky Sports colleague, Gary Neville.

“I love him to bits,” said the former United captain. “Rashford playing up front is fantastic – 150 games nearly at the age of 21, the potential is enormous.

“It’s actually now stepping up beyond potential to where he’ll be a top-class player. People will say ‘What about Romelu Lukaku, how does he get back in the team?’ Don’t worry about that.

“Worry about the kid that’s playing and who is going to devastate teams. He was a massive player all night and deservedly won man of the match. He’s brilliant to watch.”

It’s no coincidence that Rashford’s best run of form has coincided with being restored to his natural position under Solskjaer, having mostly been used out wide – or as a substitute – by Mourinho.

“But then we’ve got [Lukaku], so sometimes he (Rashford) will play on the right, sometimes on the left, sometimes through the middle. He’ll get enough games,” Solskjaer said.

United’s legendary striker would be foolish to restore Lukaku to the status of first-choice No 9, though. The Belgian can count himself lucky that his opening goal, a poacher’s finish just 38 seconds after coming off the bench, masked some pretty shocking contributions.

In the build-up to Rashford’s goal, Lukaku listlessly gave the ball away in his own half with a trademark poor first touch. Instead of chasing the ball down, he lazily stood still and watched his teammates tidy up his mess.

United won the ball back and countered again. Rashford started the move by sending it wide to Lukaku, who fluffed his control – surprise, surprise – and passed it back behind his teammate. Rashford then did well to dig the ball out first time and send Lukaku away down the right.

Once again, Lukaku passed the ball behind a teammate, this time Alexis Sanchez, but the Chilean expertly adjusted his body to turn and find Rashford, who doubled the lead with a composed finish Solskjaer would have been proud of in his playing days at United.

“I think working on composure is key,” Rashford told Sky Sports. “We haven’t had chance to work on it properly yet, but just having those words around you it makes a difference and I want to improve and keep learning.”

Solskjaer has repeatedly said he knows the importance of nurturing United’s academy talents. In Rashford, he might have the best one since Neville’s “Class of ’92”, and a player who can land him the United manager’s gig full-time if he keeps playing him over Lukaku.