Haji Mnoga became the second-youngest debutant in Pompey post-war history after appearing against Crawley last night.
The former Trafalgar School pupil only signed first-year scholarship forms with the Blues in June.
Yet he was handed a first-team introduction in the 1-0 Checkatrade Trophy triumph at the Broadfield Stadium.
Featuring at right-back, Mnoga turned in a solid and highly-encouraging display for Kenny Jackett’s men.
He featured for 65 minutes before replaced by Tom Naylor as the Blues booked their place in the second round of the competition with a group game to spare.
And aged 16 years, five months and 24 days, the academy have supplied yet another player into the first team, while team-mate Freddie Read was an unused substitute.
Now Pompey’s boss is challenging the youngster to maintain his development following such an early breakthrough.
Jackett said: ‘We want to be giving our squad players the time on the pitch, which was the right thing to do last night and, wherever possible, the odd promising youngster.
‘Haji is very young, he has a long road to go to reach where he wants to go – which is a pro footballer and a Portsmouth first-team player.
‘It’s a long road ahead of him, but he has good talent. He now has to ally that to discipline, hunger and dedication, which are really big things and something that, as a young player, you have to pick up and pick up very quickly.
‘There are a lot of people here who will work hard at keeping his feet on the floor, but he should be encouraged by last night's performance.
‘He must also take the lead off some very good professionals here and the way they do things – and how he wants to conduct himself.’
Mnoga is 15 days older than Joe Hancott, who became Pompey’s youngest post-war player in August 2017.
That arrived in a Checkatrade Trophy 3-3 draw with Fulham Under-23s, although the left-back has yet to add to that outing.
Mnoga, who can operate at right-back or centre-half, was one of eight new academy intake in the summer and is the second-youngest of Mark Kelly’s group.
During pre-season, he appeared in Pompey XI fixtures against Gosport and then Bognor.
– NEIL ALLEN