Peterborough, who only secured a top-six spot on the final day, stormed to a 4-0 victory in the opening fixture at London Road on Friday.
Match preview
When MK Dons narrowly missed out on automatic promotion last season, the disappointment was too much to handle in the playoffs as they bowed out in the semi-finals.
That is what seems likely to occur with Sheffield Wednesday, the Owls succumbing to an unforeseen drubbing in the first leg to put them on the brink of another year in League One.
Darren Moore's team had gone into that fixture on a four-match winning streak, conceding just two goals in the process, but they were blown away by a clinical Posh outfit who scored twice in each half.
While Sheffield Wednesday are no strangers to conceding away from home having twice shipped at least three goals since March 21, the Yorkshire giants were left stunned as their promotion hopes were left hanging by a thread.
Moore witnessed his side edge out Peterborough 1-0 in the corresponding fixture during the regular season, yet he is required to rip up previous game plans in search of goals on Thursday night.
From Peterborough's perspective, there is a sense that the hard work is done, Darren Ferguson appreciative of the level of performance that his players produced at London Road.
Nevertheless, Ferguson will stress that building momentum could be crucial ahead of a likely final date with Barnsley or Bolton Wanderers, Posh now posting two notable wins in succession.
Equally as important, Peterborough have kept three successive clean sheets since the 3-0 drubbing at the hands of Ipswich Town, a show of character that may have even surprised Ferguson after four games without a shutout preceded that streak.
Jack Taylor and Jonson Clarke-Harris, who now has 27 third-tier strikes for the campaign, have netted in each of their last two outings, but Posh have enough goals and creative talent in their squad where other players could chip in with what would effectively be a tie-clinching goal.
Sheffield Wednesday League One form:
L
W
W
W
W
L
Peterborough United League One form:
L
W
L
D
W
W
Team News
Moore may feel that switching to a more unfamiliar back four is his only option, with either Dominic Iorfa or Michael Ihiekwe dropping out of the Wednesday XI.
Reece James may be risked at left-back after minimal game time in recent weeks, allowing Marvin Johnson to be used further forward.
While Moore has a number of alternatives in central midfield, Will Vaulks and Barry Bannan are likely to get the nod.
Barring any fitness issues, Ferguson may see no reason to make any changes to his Peterborough starting lineup.
Ferguson has made just alteration in each of the wins over Barnsley and the Owls, and a view may be taken that players can be rested in the closing stages if Peterborough put the tie out of Wednesday's reach.
Sheffield Wednesday possible starting lineup:
Dawson; Palmer, Iorfa, Flint, James; Vaulks, Bannan; Windass, Paterson, Johnson; Smith
Peterborough United possible starting lineup:
Norris; Ward, Kent, Edwards, Burrows; Kyprianou, Norburn; Poku, Taylor, Mason-Clark; Clarke-Harris
We say: Sheffield Wednesday 2-1 Peterborough United (Peterborough to win 5-2 on aggregate)
All things considered, this tie feels over, but that will not stop Sheffield Wednesday from going all out for victory. The Owls may get the opening goal at Hillsborough, yet Peterborough should be able to manage the game efficiently enough to ensure that they book their spot at Wembley.