Pars boss John Potter has urged his faltering team to turn their poor form around before it is too late.
Dunfermline were out-classed, out-fought and out-thought at Stair Park on Saturday, losing 5-1.
The result sees them slip to sixth in League One, nine points outside the play-offs and 13 off top spot.
Potter said: “We have to win games, it is as simple as that. We have not done it the last three or four weeks and we have got to start winning games of football.
“We’re not doing that at the moment, so we will need to work hard to make sure we can in the future.”
Stranraer took the lead when Grant Gallagher fired through Ryan Scully’s legs after just 10 minutes.
The Pars found a leveller when Andy Geggan’s header from 10 yards crept inside the post.
Any chance of Potter’s side taking something from the game was dealt a severe blow three minutes later. Gregor Buchanan tangled with Jamie Longworth. After consulting his assistant, referee Kevin Graham sent off the defender for an alleged stamp.
Stranraer piled the misery on the visitors as Chris Aitken curled home a delightful effort from the edge of the box two minutes later.
Former East End Park favourite Willie Gibson repeated the trick just before half time.
Potter said: “The sending off has totally changed the game, it’s killed us.
“Gregor is adamant that he could not move and that he had to get out of the way.
“The referee said that to the players but the linesman has sent him off.
“I don’t know, I’ve not seen it again and I’m just going on Gregor’s word.”
It was game over when Scully failed to hold on to Craig Malcolm’s effort and Longworth slid home five minutes after the restart.
The Pars did have chances in the second half, with Michael Moffat firing wide and the impressive Lewis Allan striking the post.
But it was the hosts who had the last laugh when substitute Jon McShane fired home with seven minutes left to wrap up Stranraer’s biggest ever win over their opponents.
Potter said: “Everything about today was horrible.
“It’s my worst day, obviously, as a manager and the players will be hurting and it is a hard one to take.”