After both going scoreless in the first legs of their semi-finals, the Whites trounced Norwich City in the reverse fixture, while the Saints sent West Bromwich Albion packing to move one game away from reclaiming their top-flight status.
Match preview
Reverting to their winter selves at the most opportune time, Daniel Farke's Leeds had lost their way in the closing stages of the Championship season to cede the final automatic promotion place to Ipswich Town, and there was no way through for the Whites at Farke's old stomping ground Carrow Road on May 12.
However, a clever free kick from Ilia Gruev sparked a four-goal rush just four days later, as Joel Piroe and Georginio Rutter also got in on the act in a first-half whitewash at Elland Road before Crysencio Summerville capped off a magnificent second-leg display in the final quarter of the match.
As David Wagner cleared out his Canaries office, Leeds rejoiced in reaching a playoff final for the fourth time in their history, but the omens are not promising for the more superstitious Whites fans, who have never seen their side earn promotion in such circumstances.
Indeed, Leeds lost their playoff finals in the 1986-87, 2005-06 and 2007-08 campaigns, and no side has ever suffered more defeats in such matches than the Whites, whose total of three is level with Bristol City, Exeter City, Lincoln City and Shrewsbury Town.
As such, unwanted playoff history will be made for Leeds if their winless streak in finals stretches to four from four matches, and the thrashing of Norwich being just their second victory from eight games is hardly a morale-boosting statistic either. Alternatively, they may have rediscovered their fire at the pivotal moment.
Leeds' second-leg success was akin to that of upcoming foes and fellow 2022-23 Premier League relegation victims Southampton, who came away from West Brom's Hawthorns base with a creditable goalless stalemate to their name before running riot on St Mary's soil.
Rather than blow their visitors away in the first half, though, Will Smallbone's tidy 49th-minute strike preceded a brace from the inevitable Adam Armstrong, and even though Cedric Kipre wiped out the Saints' clean sheet, his looping header in the seventh minute of added time only triggered muted cheers from the Baggies faithful.
Sharing another similarity with their Wembley opponents, Russell Martin's side have also consigned a troubled end to the regular season to the past after losing three of their last four fixtures, and a first-ever playoff final now awaits the South Coast outfit, whose only previous post-season adventure ended on penalties to Derby County in 2007.
Furthermore, only twice before has a second-division playoff final been contested by two sides that were relegated in the previous campaign, as West Ham United edged out Blackpool in the 2011-12 edition, 16 years on from Leicester City's identical beating of Crystal Palace.
A ticket to the English elite with the Foxes and Ipswich will fall into the hands of Sunday's victor, and the playoff final comes just 22 days after Southampton left Elland Road with a 2-1 win to their name, thereby completing a league double over Leeds courtesy of a 3-1 home success back in September.
Leeds United Championship form:
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W
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Southampton Championship form:
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Team News
As well as the known absent trio of Patrick Bamford (knee), Darko Gyabi (groin) and Pascal Struijk (groin), Leeds also had to make do without Sam Byram for the four-goal crushing of Norwich owing to a hip injury, which has rendered him doubtful for the playoff final as well.
Bamford is in the exact same boat and should certainly not be risked from the start even if he is given the green light to make an appearance, while Struijk and Gyabi are both on the mend from season-ending operations and will watch on from the sidelines.
Regardless, Farke will surely see no reason to alter the Whites' winning formula, thereby persisting with the highly-rated Archie Gray at right-back amid reports that Bayern Munich have taken a liking to the teenage phenom.
Likewise, Southampton boss Martin is also coping with a trio of long-term victims, including hamstring pair Juan Larios and Stuart Armstrong, while goalkeeper Gavin Bazunu is on the mend from a ruptured Achilles.
Ryan Fraser - omitted from Scotland's provisional squad for Euro 2024 - was also forced off the field on the 66-minute mark against West Brom, although he is not thought to be carrying a serious issue and should be fine to reprise his role in the XI.
As is the case with Leeds, Saints boss Martin has no need to tinker with his starting XI at Wembley, in spite of the fact that Fraser's replacement against West Brom - Ryan Manning - won the penalty for Armstrong to convert his second of the night.
Leeds United possible starting lineup:
Meslier; Gray, Ampadu, Rodon, Firpo; Gruev, Kamara; Gnonto, Rutter, Summerville; Piroe
Southampton possible starting lineup:
McCarthy; Walker-Peters, Harwood-Bellis, Bednarek, Stephens; Aribo, Downes, Smallbone; Brooks, Armstrong, Fraser
We say: Leeds United 2-2 Southampton (a.e.t, Southampton to win on penalties)
Having both rekindled the attacking flame after underwhelming ends to their regular season, the leash should come straight off Leeds and Southampton's fired-up attackers at Wembley, where goals are surely a guarantee.