Pompey Academy’s winless run stretched to five games with a 5-2 defeat at Cheltenham.
There were a flurry of goals just before the break, with George Lloyd’s penalty for the hosts breaking the deadlock.
Leon Maloney (pictured) then latched onto a ball over the top and neatly lobbed the keeper for an impressive equaliser.
But the Robins struck twice more through Archie Brennan and another Lloyd spot-kick to end the first half with a commanding lead.
Jack Beardsell increased their advantage further after the interval, only for Dan Smith to hit back with another penalty after James Whiting had been brought down.
Pompey tried to make more inroads, but were caught on the break by Ben Hailwood as Cheltenham wrapped up a convincing victory.
Lead professional development phase coach Mikey Harris said: “It was obviously a really disappointing day from our point of view.
“The scoreline doesn’t reflect the amount of possession we had, but Cheltenham were certainly the better team in both boxes.
"Too many of our players didn’t do their jobs – either with or without the ball."
“We were extremely poor by our standards and although we got into the final third on plenty of occasions, there wasn’t enough quality to make that count.
“I felt that both of the penalties awarded against us were soft, but they came about because of our sloppy defending.
“Too many of our players didn’t do their jobs – either with or without the ball and ultimately that cost us.
“So they have to reflect on that performance and learn from what happened. We’ll watch the game back and try to pick the bones from it.
“It’s important that the lads learn from their mistakes and work hard in training, so that we see a response next Saturday.”
Pompey: Collins; Chandler, Casey, Brooks, Hancott; Read, Johnston (Smith 66); Whiting (Stanley 75), Maloney, Flint; Mayes (c)
Subs not used: Birchnall, Mnoga, Burroughs