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...
5. Regan Poole - 7
Back in the side after a two-game absence with an ankle injury and produced one crucial block to deny Brewster’s goal-bound first-half attempt. As ever, full of fight and heart. Photo: Graham Hunt
6. Jordan Williams - 5
Came in at left-back in Swanson’s absence and, crucially, lost Ward in the build-up for Derby’s equaliser on the stroke of half-time. Had a great second-half chance to tee up Segecic, but produced a poor pass. Photo: Dan Istitene
7. Andre Dozzell - 7
Found himself with another central midfield partner, with Kosznovszky alongside him this time. Booked late in the first half after pulling back Agyemang to prevent a counter-attack. Spent much of his time chasing and harrying rather than dictating play. Photo: Graham Hunt
8. Mark Kosznovszky - 6
(Replaced by Marlon Pack on 66 mins) Chosen ahead of Pack and Swift in the centre of midfield, the Hungarian was again neat and tidy, keeping things simple. Awful misplaced pass on 31 minutes almost gifted Derby a goal, but Schmid rescued him. Photo: Simon Roe