Pompey fell to their second frustrating away defeat on the bounce at Hull.
Robert Koren’s 11th-minute 30-yarder was the difference between the two sides at the KC Stadium in a 1-0 loss.
And Luke Varney’s second-half dismissal compounded Pompey’s misery, after he was given a straight red for a challenge on James Chester.
It looked as if Jamie Ashdown should have done better with the dangerous Koren’s decisive strike.
But Steve Cotterill’s men had the keeper to thank for keeping them in it with a string of fine saves.
Ashdown denied the lively Robbie Brady on a hat-trick of occasions.
Pompey looked to be getting back into the game after being largely second best following a switch to a 4-4-2 system.
But then Varney walked after his lunge on Chester with 12 minutes left.
That put paid to Pompey’s hopes of getting back into the equation.
Their best chances fell to the industrious Benjani who put two early headers just wide.
David Norris bundled Adriano Basso over the line after another Benjani header in the second-half - but that was rightly ruled out.
The result leaves Pompey in 18th place on six points.