Pompey, who have been in administration for more than a year, finished Tuesday night's 1-1 draw against MK Dons with four Academy graduates in their side.
Ashley Harris came on with 15 minutes remaining to join fellow homegrown youngsters Dan Butler, Jed Wallace and Adam Webster, the first time all four had appeared in a league game together.
Whittingham said: "That's the future of the club. They were all in the development group at the start of the season or last season and we've got to carry that on.
"This club is going to need those sort of homegrown players and we're making sure they have the opportunity to be there on the pitch.
"We need the young players here to see that there is a path through to the first team."