Guiu scored 33 seconds after coming on for his debut

The teenager is far from the typical Barca academy product, with teammates Lamine Yamal and Gavi making their senior bows at an earlier age.

Guiu stands out from the modern La Liga strikers and may have been fearing that a pathway to Camp Nou would have been blocked.

He is strong, fast, and direct with his strengths being playing on the shoulder rather than dropping deep to link up with midfielders.

However, an injury to Robert Lewandowski opened the door for Xavi to turn to him with Barcelona struggling to beat Athletic Bilbao on Sunday.

Guiu was introduced with just over 10 minutes left at the Olympic Stadium and took just 33 seconds to latch onto a pass from Joao Felix and slot home to seal a 1-0 victory.

The Spaniard, dubbed ‘a striker in the shadows’, by Sport, has now written himself into the club’s history books having scored his first league goal for Barcelona quicker than any other player.

Barcelona manager Xavi said: “I told him he would have one good chance. I love seeing the face of these kids. They have no fear.”

He produced a finish Robert Lewandowski would have been proud of

Guiu was mobbed by his teammates after announcing himself on the big stage

“I can’t believe it, I’m short of breath,” Guiu said afterwards. “I’m enjoying the moment. This is unimaginable, but I’ve been working all my life to take advantage of opportunities and it’s come to me.

“Inigo [Martinez] has told me I won’t be able to sleep, but to enjoy it.”

Guiu won’t have much time to enjoy it, with Barcelona gearing up for their biggest game of the season this weekend.

Spanish giants Barcelona and Real Madrid clash in the first El Clasico of the season on Saturday.

Although Lewandowski’s return has meant Guiu will have to return to the bench, the boyhood Barca fan will be desperate to make an impact against his club’s arch-rivals.

Born in 2006 less than an hour from Camp Nou, Guiu started playing football at a supporters’ club at the age of 5.

Within two years he made the switch from Penya Barcelonista Sant Celoni to establish a foothold in La Masia’s set-up by 2014.

Guiu’s age group has been hailed as one of the most talented crops of Barca talent but top prospects Alexis Olmedo and Hector Fort are still awaiting their chance.

Guiu worked hard to establish himself in a talented La Masia set-up

Former Barcelona coach Ivan Carrasco, who coached Guiu in the youth ranks, told SPORT: “I was very happy for Marc, he deserves it because he is a ten as a person. He’s a sensational boy, a hard worker, an example as a team-mate for his effort and dedication.

“He is a pure centre forward, a classic ‘9’, a specialist in the area who lives from his physical power. His best virtue is his aerial play. Marc is also very quick and powerful, he is unstoppable with space.

“He is not a striker who can drop to the flanks or stands out for his combination play but he is aware of his strengths and limitations and knows how to focus on his strengths and hide his flaws.

“Another of his virtues is his great ability to fight for every ball and press like an animal, defenders are not comfortable with such a hard-working striker profile”.

He got his big break for Spain’s U-17 side

Guiu has also caught the eye on the international stage after scoring four goals as Spain reached the Under-17 European Championship last summer.

His tally at the tournament was matched by close friend Yamal, who was on the pitch alongside him on Sunday for his famous goal.

But it was the presence of fellow teammate Joao Cancelo who brought Guiu back down to earth after his strike.

Among the on-field celebrations after the final whistle, the Manchester City loanee joked: “You have to buy us a dinner now.

“You have to buy us a dinner in McDonald’s.”

Hopefully, his post-match feast hasn’t taken away his hunger to become the latest starlet to light up El Clasico…