Pompey Academy exited the Youth Alliance Cup with a 2-1 defeat to Gillingham at Furze Lane.
They broke the deadlock on 13 minutes, with Dan Smith (pictured) scoring from the spot after Matt Mayes had been brought down in the box.
But the visitors stole possession to draw level before the break and then snatched a winner in the second half.
Lead professional development phase coach Mikey Harris said: “We were okay in the first half and controlled possession, although not as much as we would have liked.
“We went ahead from the spot, but then gifted Gillingham an equaliser. We do encourage the boys to play out, however, so have to appreciate that they will be caught out on occasions.
"We certainly fell short of the standards that we set ourselves."
“It was disappointing to then concede from a set-piece, as that’s something we work very hard on in training.
“We’re more frustrated with the performance than the result because we certainly fell short of the standards that we set ourselves.
“The way Harry Kavanagh and Alfie Stanley played was a big positive, though – they were both excellent after stepping up from the under-16s for their first starts.
“It’s a busy period for the boys at the moment and we have our third game in a week on Friday, so hopefully we’ll see a response at Plymouth and continue our good start to the league campaign.”
Pompey: Collins; Kavanagh (Chandler 46), Brooks, Dandy (Casey 46), Flint; Whiting, Smith (Hancott 46); Maloney, Stanley (Read 46), Johnston; Mayes (c) (Lethbridge 46)