Jake Jervis struck the only goal of the game as Pompey battled their way to a 1-0 win over fellow League Two strugglers Accrington Stanley.
The striker thundered in a low drive three minutes into the second half, after the Blues turned in another poor first-half showing.
Pompey boss Richie Barker rung the changes, with five new faces in the side after the 5-1 drubbing at Scunthorpe on Saturday.
But while the home side were less than convincing in the first period tonight, they were much improved after the break.
And after going ahead, they were largely untroubled at the back as they claimed a much-needed three points to give themselves some more breathing space in the battle to stay in League Two.