Pompey suffered a second successive League Two defeat as they went down 2-0 to high-flying Burton Albion.
Goals from Adam McGurk and Lucas Akins proved the Blues’ downfall as the latter was a thorn in their side all afternoon at the Pirelli Stadium.
The giant striker had a hand in the opener on 85 seconds, robbing the ball from Danny Hollands before passing to Stuart Beavon, who set up McGurk for a back-post tap-in.
And he showed his eye for the spectacular when he smashed a left-foot drive past Pompey keeper Paul Jones after a quick turn on the edge of the box on 56 minutes.
In between, Andy Awford’s side did their utmost to get back on level terms, with the hosts forced on to the back foot to protect their lead.
Jed Wallace’s volley on 17 minutes had Burton worried – as did Ryan Taylor’s overhead-kick that fell into the arms of home keeper Jon McLoughlin.
Craig Westcarr and Hollands also tried their luck in front of the goal as Pompey looked to rectify the early damage.
That determination was shown again after the half-time interval when Taylor saw his shot blocked and Alex Wynter was denied twice from close range by the alert McLoughlin.
But the visitors were soon made to pay for their inability to convert their possession into goals when Akins brilliantly struck 11 minutes after the restart.
Pompey attempted to salvage something with the second-half introductions of Miles Storey, Patrick Agyemang and Dan Butler.
But despite snapshots from both James Dunne and Hollands, McLoughlin’s goal was rarely troubled.
Burton climbed to the top of the table on 16 points, leaving Pompey playing catch-up in ninth position with 10 points from their opening six League Two fixtures.