Guy Whittingham has challenged Pompey’s boys to become men if they want to avoid contracting the second season syndrome.
Last term marked a breakthrough campaign for four Blues youngsters who found themselves regulars in the first-team squad.
Teenagers Jed Wallace, Ashley Harris, Adam Webster and Dan Butler made 91 appearances between them.
Having put that foot in the door, Whittingham is now looking for the quartet to march on and enhance their reputations.
Football is littered with prodigious talents who failed to build on that first season.
And Pompey’s boss has called for Wallace, Harris, Webster and Butler not to suffer a similar fate.
He said: ‘This is the difficult second season and all our young lads have to grab the bull by the horns.
‘After a testing first season you normally get young pros coming back thinking “I have made it as a footballer”.
‘Well, I can tell you, you’ve had the easy time up to now – now you are in the mix with people aged up to 36, 37 and 38. You are in a big pond now.
‘You have to prove you are worth it. If you are not, then you slip out and that’s it – you start going downhill.
‘With Ash, Dan, Jed and Adam they all have to really push on and show people they are good players.
‘The first season would have been viewed as nothing to lose.
‘People aren’t expecting too much of them, so they will have been told to go out and just enjoy themselves. Work your socks off and give 100 per cent.
‘Now that 100 per cent isn’t enough. You have to play well with the ball as well.
‘I think that is the difference when you go into your second season in your professional career.
‘You have to prove you are a good player and not just that you will work hard on the football pitch.
‘It is all about attitude to training, all about desire to make themselves better, all about making sure they are the best athlete they can be because the game is very physical.’
Of the quartet, Harris made the most appearances – although 20 of his 29 games came from the bench. Wallace earned the most plaudits following his six goals in 23 matches, while Butler made 16 starts and two substitute appearances.
Webster, who is now a first-year professional, played 21 times.
Whittingham added: ‘They will get all the help they need.
‘But as a pro now they need to do it themselves rather than being told when they have got to do it.
‘Now they have got to come to the coaching staff and say “I want to do a bit extra” or “I want to go to the gym, what is going to help me?”.
‘But they have to come to us.
‘They have got to step up to it and keep on that desire now.’