Guy Whittingham sent Adam Webster out on loan but vowed ‘to keep the numbers up’.
Ashley Harris could follow Webster out of the door at Fratton Park, as the defender completes his switch to Aldershot.
Webster, 18, will move to the Conference National side until the end of the year in a bid for playing time.
Harris may now go down the same route after the duo missed out on being in the Pompey squad for the League Two curtain-raiser against Oxford.
But Whittingham believes it is crucial he keeps the squad at a workable level – and any departures are replaced.
He said: ‘Adam needs to go out and play games.
‘He’s 18, that’s what people forget. He’s been around us for two years now but he’s a young kid who needs to learn the game. Adam’s a level-headed lad and there is a great opportunity for him to go out and get experience.
‘As we know it’s important to have a decent squad.
‘I want a squad of 20 and I will always say to the chairman we need a couple more. You have to keep that one going!
‘We got Bondz N’Gala because Adam was going out.
‘If Ashley or one of the young lads go out now we have to replace them because we need to keep the numbers up.’
Whittingham is keen to repeat last year’s formula when development squad players were loaned out.
He said: ‘There could be others among all the young players to go out.
‘They are young pros, so they have to learn about the game.
‘There is the development squad and Ashley – they need to play games.’