Colby Bishop headed home Joe Morrell’s right-wing cross to open the scoring in the 24th minute, albeit completely against the run of play.
It marked a transformation in the Blues’ game, with John Mousinho’s side suddenly looking the better side, and it continued early into the second half.
However, substitute James Collins levelled with 19 minutes remaining and the match finished 1-1, with Derby’s disappointment obvious as they push for play-off qualification.
Yet there were some sterling performances among Pompey’s players and here are our ratings...
9. Conor Chaplin - 5
(Replaced by Adrian Segecic on 66 mins) Always wants the ball, always encouraging, team-mates, always on the move, but it just didn’t happen for him. Too careless in possession at times and a real off-day. Photo: Stephen Flynn
10. Josh Murphy - 6
(Replaced by Harvey Blair on 53 mins) Forced to come off through an injury, indicating to the bench he needed to be substituted after his left-wing cross landed on the roof of Derby’s net. Had largely been quiet up until that point, other than supplying the pass for Lang to open the scoring from. Photo: Graham Hunt
11. Callum Lang - 8 - MOM
Should be next for a new deal. Restored to the right wing and opened the scoring after cutting in from the right and finishing with his left foot. His energy, drive and determination was a constant threat, never allowing Derby defence to settle. Photo: Graham Hunt
12. Colby Bishop - 6
Recalled to the team and had a terrific battle with Dion Sanderson which showed the value of having a physical centre-forward. His clever lay-off also played a key role in the build up for Pompey’s opener. Photo: Graham Hunt