Pompey Academy dropped out of the Youth Alliance League title race after falling to a 2-0 defeat at Bournemouth.
Marcus Daws opened the scoring from the penalty spot after Lewis Brown was adjudged to have been fouled in the box.
And Baylin Johnson then doubled the hosts’ advantage by completing a neat move midway through the second half.
Professional development phase coach Liam Daish said: “We stressed beforehand that – after the result on Saturday – we had to defend our goal better and show more responsibility.
“For long periods of the game we did exactly that, only to concede from a dubious penalty in the first half.
“We showed more aggression in the way we closed Bournemouth down after the break because we needed to get a yard closer to them.
“I also felt there was more identity and a competitive edge, which was something we had stressed to them.
"We spoke to the boys about what a Pompey team is all about and that there can’t be an acceptance of being second best – individually and collectively."
“We spoke to the boys about what a Pompey team is all about and that there can’t be an acceptance of being second best – individually and collectively.
“So I was pleased to see us start to put our opponents under a bit more pressure and not show them quite so much respect.
“There were times when we won the ball in their half, although our calmness and control in possession wasn’t up to the standard that was required.
“The second goal we conceded was probably against the run of play, but we need to keep making the boys aware that this is a competitive industry they’re in.
“We did blood quite a few 16-year-olds, as we’ve done in recent weeks, and they’re getting a taste of being a scholar ahead of next season.
“It means that they’re becoming more aware of what it’s all about and hopefully this time in the under-18s side lets them know what to expect.”
Pompey: Steward; J.Fox, Kaba, Dockerill, Bridgman; Aston, Jewitt-White, Simpson (Bosaka 74); Kamavuako (Trialist 74), Hurst, Howell (Laidlaw 46)