Pompey’s survival hopes were dealt a devastating blow as they were crushed by Burnley.
Michael Appleton’s side went down to a 5-1 thumping to the Clarets at Fratton Park.
That gives them a mountain to climb in their bid to stay in the Championship this season.
Burnley took the lead against the run of play after 16 minutes when Kieran Trippier blasted in Chris McCann’s corner.
The Blues levelled three minutes later when David Norris rifled in Luke Varney’s cross.
It looked set for Pompey to take control of the game, but Burnley took the lead through Danny Ings’ header two minutes after the restart.
And that paved the way for a total collapse as edginess crept in to the crowd and the home side’s game.
Sub Charlie Austin helped himself to hat-trick after entering the fray.
He looked to handle his opener after 74 minutes, but then grabbed two more in stoppage time.
Jason Pearce played a short backpass to Jamie Ashdown which Austin took advantage of.
Austin then finished a breakaway with a tap in as the Clarets got their first win in seven in the most emphatic style.
Pompey are now five points from safety with six games left.