Watch key moments from Fratton defeat
A 2-1 loss at home to Northampton means Pompey will be at home in the first leg of their play-off clash with Plymouth.The League Two champions took the lead when Jack Whatmough inadvertently sliced Nicky Adams' cross into his own net.
Kieron Freeman was then sent off for a late challenge early in the second half, only for Kal Naismith's stunning long-range strike to draw the Blues level.
But it was the visitors who secured victory late on, as James Collins turned home David Buchanan's cross.
Watch the key moments from the game below or subscribe to Pompey PlayerHD for extended highlights.