A youthful Pompey Reserves side fell to defeat in an insipid Premier League Cup clash with Barnsley at Westleigh Park.
Defender Drew Talbot was the only non-teenage player for the hosts in their third group stage fixture.
It looked like the points were going to be shared, only for Jacob Brown to grab a last-gasp goal for the Tykes.
The visitors were first to try their luck, although Louis Wardle’s effort was comfortably gathered by Alex Bass.
Pompey’s keeper had a more demanding save to make soon after, parrying Victor Adeboyejo’s close-range attempt to safety.
And the Blues should have done better at the other end when the ball had only been partially cleared, with Theo Widdrington’s shot clearing the crossbar by some distance.
It was Barnsley who looking the more threatening side in the opening stages, without being able to showcase any cutting edge in the final third.
But Pompey were showing signs of settling into the contest as the half progressed, even if another Widdrington strike flew well off target.
The game was bereft of any clear-cut openings and the hosts tried to force the issue just before the break.
Jack Walton was twice called into action for the Tykes, first keeping out Dan Smith’s angled effort and then denying Leon Maloney.
Half Time: Pompey 0 Barnsley 0
When the action got back underway, Romal Palmer sent one shot straight down the throat of Bass, while a second flew over.
At the other end, Widdrington picked up the second ball from his own corner and saw his attempt deflected wide.
There were still not many chances of note, though, and Jared Bird’s free-kick was well off target after Ben Williams had been brought down by Matt Casey.
Pompey’s best chance of the match came when they broke quickly from a Barnsley corner, although Walton came racing off his line to stop Smith from rounding him.
The hosts had been resilient if nothing else, but were cruelly denied a share of the spoils in the 89th minute.
Williams whipped in a corner and an unmarked Brown made no mistake to settle a contest that did not really deserve a goal.
Pompey: Bass; Talbot, Dandy, Casey, Hancott; May (c) (Johnston 83), Widdrington; Smith, Maloney (Lethbridge 55), Bedford; Mayes
Subs not used: Pitman, Brooks, Read
Barnsley: Walton; Smith, Fielding, Lund, Williams; Wardle, Bird (c) (Dolan 78), Wolfe, Palmer; Adeboyejo, Brown
Subs not used: Tingle, Miller, Swinburn, Ocran
Referee: Adam Penwell