Jim Jefferies believes it is vital his Dunfermline side beat St Mirren on Saturday to have any hope of Clydesdale Bank Premier League survival.
The Pars have five games to overcome a seven-point deficit to second bottom Hibernian, the William Hill Scottish Cup finalists.
The two teams fighting for survival are scheduled to meet in the penultimate game of the season, but Dunfermline's fate would be sealed by then if they do not soon end the 11-match winless run dating back to January 21.
"It's crucial," said Jefferies of the first post-split fixture in Paisley.
"I think to have any realistic chance we've got to win it.
"If we don't win it and even if Hibs don't win their game, it's a big advantage for Hibs, because it's another game out of the way, you've only got four games left. "What we need is a win and for Hibs to lose.
"We're favourites to go down so the pressure should be off a little bit.
"We've got to make sure everyone here believes we've still got a chance and while it's mathematically possible you've got to go for it.
"But we have to win on Saturday."
Hibs, who host Kilmarnock on Sunday, are buoyed by an unbeaten three-match run which has seen them extend their advantage over the Pars and advance to a Scottish Cup final against Edinburgh rivals Hearts on May 19.
Jefferies, who began the season as Hearts boss, anticipates Hibs' progress in the cup will aid their bid for SPL survival.
He added: "They won't be easing up. They're in a good position, they've got momentum and getting to the cup final will help their confidence."
Midfielder Paul Burns and striker Steven McDougall are available again for the Pars, while midfielder Nicky Phinn is nearing a return after two friendly appearances following a troublesome hamstring injury.
"Saturday's come too quick for him, but if he gets a full game under his belt we might have him for a couple of games for the run-in," Jefferies added.
Meanwhile, Jefferies has offered striker Kevin Kyle the opportunity to train with the Pars in future.
Kyle recently left Hearts after battling a hip injury but played under Jefferies at Kilmarnock and at Tynecastle.
"Kevin's got to concentrate on getting himself fit for the new season," Jefferies said.
"There has been some suggestion that he might have a deal with Hearts to try to go back there.
"I said to him if it doesn't work out then he could come and train here. That's all it was."