He played for only three minutes, and he did not touch the ball even once as Manchester United lost to Tottenham Hotspur on Sunday, but for Chido Obi it was still the most momentous of occasions. A Premier League debut, at the age of just 17. The young striker has a long way to go but he has now taken the first significant step towards fulfilling his considerable potential.

It was rather poetic, too, that Obi’s first senior appearance came in north London, just a few miles down the road from where he began his life in English football. Obi spent two years in Arsenal’s academy, where he was regarded as one of the club’s most exciting prospects before he decided to leave for United last year.

Also on Ruben Amorim’s bench at the Tottenham Hotspur Stadium was another teenager who has recently moved to Old Trafford from Arsenal: defender Ayden Heaven. The 18-year-old transferred in the winter window, for a fee understood to be more than £1.5 million.

Of the two, it will be the sight of Obi in United’s kit that will trigger the most frustration at Arsenal. The loss of the striker is a source of considerable irritation for the club’s executives, who were aware of Obi’s talent and had worked hard in their attempts to keep him. Mikel Arteta is believed to have personally intervened, to no avail.

Why did Obi choose to swap Arsenal for United at this crucial stage of his development? One reason, it is understood, is that he and his advisers had concerns over his pathway to first-team action at the Emirates. Another potentially relevant factor is that United were willing to go significantly further with their financial offering than Arsenal.

Arsenal are believed to have presented a plan to Obi that had him transitioning from the under-18 team to the under-21s during this campaign, with opportunities to join first-team training. The player wanted to progress faster, having already demonstrated his ability at under-18 level. Last season, after all, he scored a remarkable 32 goals in just 18 under-18 games.

Arsenal’s annoyance at his departure will not have been eased by his form since, as the powerful forward has continued to score goals at youth level. After signing for United in October, he struck a hat-trick within 15 minutes of his debut for their under-18s. He has also scored seven goals in three FA Youth Cup matches this season.

To an extent, Obi’s first-team debut on Sunday means he has been proven right in picking the United pathway over the route offered by Arsenal. The counter-argument is that Arsenal’s current striker injury crisis would probably have opened the door for him had he stayed.

After losing such an exciting prospect to a rival club, it was far from ideal for Arsenal to then lose another one, to the same team, a few months later. The situation with Heaven, though, is markedly different to Obi.

Arsenal had made an offer to Heaven but their executives, it is understood, were ultimately comfortable with his departure. The defender played for 10 minutes in Arsenal’s League Cup win at Preston earlier this season, but it was always going to be a tough ask to break into the first-team fold any time soon.

Ahead of Heaven in the centre-back pecking order were Gabriel Magalhaes, William Saliba, Ben White, Jurrien Timber and Riccardo Calafiori. Regular action with the senior side was therefore a long way off, if Heaven was even deemed ready for it.

For Arsenal, the loss of Obi and Heaven has fuelled concerns among supporters that the club do not show enough faith in youth. This was an increasingly widespread grumble last summer, when promising defender Reuell Walters and winger Amario Cozier-Duberry both chose to leave. A few months earlier, defender Lino Sousa had moved to Aston Villa.

The loss of these players caused fans to worry that the club were struggling to retain their best talents, and that Arteta was not providing academy starlets with enough opportunities in the first-team set-up.

Since then, Arteta has provided the best possible riposte by consistently backing the teenage pair of Ethan Nwaneri and Myles Lewis-Skelly. The suggestion that the Arsenal manager does not trust academy players has been blown out of the water by these two youngsters, who have made a combined 26 Premier League appearances so far this season.

Clearly, Nwaneri and Lewis-Skelly are deemed good enough to make an impact in first-team football at this stage of their careers. Clearly, Arteta did not feel the same about Heaven, Walters, Cozier-Duberry and Sousa. Since joining Luton Town last summer, Walters has made 15 senior appearances. Cozier-Duberry signed for Brighton but is now on loan at Blackburn Rovers, where he has scored once in 21 games.

There is another factor at play: none of Obi, Heaven, Sousa, Walters and Cozier-Duberry had progressed through the Arsenal system from the start of their youth journey. Obi was born in Denmark and did not join Arsenal until 2022. Heaven spent the first four years of his academy career at West Ham United. Sousa came from West Bromwich Albion in 2022. Walters was at Tottenham Hotspur for four years, and then almost joined United. Cozier-Duberry signed for Arsenal when he was 14.

Nwaneri, Lewis-Skelly and Bukayo Saka, by contrast, were all in the building at the age of eight. Arsenal’s academy bosses regard the under-nine age group as the most important in the academy, partly because it creates players who are steeped in the club’s culture from an early age. Their connection to the club is often stronger than those who arrive later, which makes it easier to retain them as they develop. Nwaneri, for example, turned down more lucrative opportunities from elsewhere in order to stay at Arsenal.

Only time will tell whether Arsenal erred in failing to retain those academy players who have left. Of them all, the feeling in north London is that Obi is the one that got away. It is his departure that rankles the most, and that frustration will only grow if his debut on Sunday proves to be the start of a successful career at Old Trafford.