Richie Barker criticised Pompey’s defending after slumping to a 3-0 defeat Rochdale.
Bondz N’Gala had a header cleared off the line in the eighth minute, while Joe Devera’s squandered the follow up.
But Matt Lund broke the deadlock on 15 minutes and in the second half Ian Henderson and Peter Vincenti settled the contest.
All three goals were poor defensively – an aspect to Pompey’s play Barker thought he had eradicated.
The Blues are now two points above the relegation zone, and afterwards the manager spoke of his disappointment at his team’s carelessness.
Barker said: ‘The first goal is the really disappointing one if I’m honest because it obviously sets the tone for the rest of the game.
‘It’s two headers from a corner – Joe doesn’t win the first one and then somebody doesn’t win the second.
‘There has got to be a great desire. We didn’t win enough headers in both boxes.
‘Every time we think we’ve solved a problem and moved on to a different problem, the other problem crops back up again because of the mental capacity to take the information on board – and that is aggression to win a header in your own box.
‘It’s not as if they carved us up, it was a set-piece, two headers and a long ball where we have just not defended it.’