Grant McCann's superb free-kick helped Peterborough move out of the relegation zone as they beat fellow relegation battlers Sheffield Wednesday 1-0.
McCann curled in a brilliant effort from 30 yards to settle a scrappy game that saw Posh move above Barnsley on goal difference.
Dave Jones' Owls are just a point further ahead in the table, setting up a dramatic final day in the npower Championship.
Posh boss Darren Ferguson made five changes to the side that lost to Derby with McCann, Michael Bostwick, Grant and Nathaniel Mendez-Laing earning recalls and Alex Pritchard handed a full debut.
Wednesday started with Steve Howard in attack in place of Leroy Lita while Rhys McCabe and Chris Maguire were brought in to the midfield.
Posh were the first to seriously threaten. Chris Kirkland saved well from Lee Tomlin's drive from the left and the rebound fell for Dwight Gayle who stumbled past the Wednesday goalkeeper but Miguel Llera reacted quickly to clear away from danger.
Mendez-Laing was denied a tap-in in the 22nd minute as Danny Pugh stretched to take the ball off his head and divert away for a corner before Michael Bostwick blazed a free-kick over.
It took Jones' side 27 minutes to test Robert Olejnik - Giles Coke's sweetly-struck effort beaten away by the Austrian goalkeeper.
Wednesday caused problems from the following set-pieces and, after the Lions failed to clear a free-kick the ball fell for Seyi Olofinjana but his shot was blocked by Gabriel Zakuani.
Set pieces were causing problems for both defences and from Peterborough's next corner Kirkland was forced to punch clear as Pritchard's delivery appeared to be heading directly in.
Two minutes before the break Gayle was released down the right by Tomlin and the striker skipped past Llera but hit straight at Kirkland.
Anthony Gardner should have given the Owls a half-time lead when he stole in at the far post to get his head to Danny Pugh's corner but could only divert the ball into the side-netting from point-blank range.
Jones brought on Kieran Lee on for McCabe at the break, allowing Maguire to play through the middle alongside Howard, but the switch failed to change the contest's end-to-end nature.
Posh wanted a penalty in the 49th minute when Gayle's shot appeared to strike Llera's hand but referee Nigel Miller adjudged it to be accidental, Llera was then involved in the action at the other end as he knocked down for Howard but the on-loan striker's scuffed shot was easy for Olejnik to gather.
It was a game lacking in quality but that changed in the 64th minute as McCann stuck his free-kick in off the post to give Posh the lead.
Wednesday should have been level two minutes later when hesitation between Olejnik and Zakuani allowed Maguire in but the striker blazed his effort over the bar.
Tomlin was denied from the left when Kirkland saved well at his near post before he got on the end of a Mendez-Laing flick but his shot flew narrowly wide of the target.
The Owls wasted a glorious chance when the ball fell for Lita close to the penalty spot and after his first effort was parried by Olejnik the striker fired the rebound over.
Lewis Buxton went within inches of an equaliser in the 87th minute when his looping cross grazed the far post, before Gardner headed wide from a corner as the game entered five minutes of stoppage-time.
But Wednesday failed to score and will now need to beat Middlesbrough at Hillsborough next Saturday to ensure their survival.