Youngsters Ryan Williams, Sam Magri, Lewis Stockford and Lewis Tallack were all involved as Pompey claimed a 4-0 win at Havant & Waterlooville on Monday, but Cotterill says they will not be in the matchday squad when the Championship campaign kicks off on August 6.
Instead he feels that mingling with the first team will be a good training exercise for his fledglings.
Cotterill told the Portsmouth News: "I don't think we will be seeing them in the first-team squad regularly at the moment. They are far too young, really.
"We are talking about them being 17 years of age, they are not physically developed, they are far from being men.
"They are good young boys who have done a bit of training with us so far - and will continue to do that."