It has been five-and-a-half years since the last meeting at a wet Hillsborough. The resounding chant that has filled the air along the four-mile stretch from Bramall Lane and echoed through Sheffield's hills has been powerful.
Mind the gap.
United's climb, from the bowels of League One to within sight of Europe under one of their own, was dizzying and euphoric.
Then came the descent, lonely and brutal.
Amid the pandemic, the Blades endured the worst start to a season in English football history and Chris Wilder's tumultuous exit. Another promotion, secured this time by Paul Heckingbottom, was delivered despite a backdrop of financial strife and bungled takeover bids. That one also ended in ignominy, the journey soured by the destination.
TrendingNorth of the city, Wednesday have toiled, frequently characterised by chaos.
Almost a quarter of a century has passed since the Owls last played Premier League football. Dejphon Chansiri, the owner who once asked disgruntled fans to help him pay a tax bill, has presided over nine managers in as many years at the helm. There has been fleeting joy, like that Peterborough miracle, but dysfunctional decision-making has prolonged malaise. In 2021 came the modern-day nadir of a first double relegation.
Two proud clubs in the city with ample rights as the birthplace of football - Sheffield FC and Hallam FC played the world's first local derby in 1860 - deserve more. More than ownership uncertainty, transfer embargoes, docked points and neglected infrastructure. Still the fervour persists, through thin and frequently thinner.
Boardrooms and bank accounts will determine the long-term prognosis - United fans are waiting for news of a long-anticipated US takeover - but in the dugouts there is continuity and connection again.
Old feelings will stir on Sunday: a nauseous mix of excitement and trepidation and family bonds temporarily broken. The fixture's return is nourishment for a city that too seldom shouts of its heritage, and overdue spotlight beyond south Yorkshire. The music scene has long been rich, too, but Sheffield has always moved to the rhythms of United and Wednesday's weekends.
After three goalless draws, sparks would feel fitting.
United, top of the league form table over the last 11 games, are favourites, even though plenty from the red as well as blue side of the divide will plead: just don't lose. But a win at this juncture of the season would embolden respective promotion and top-half ambitions, as well reclaim bragging rights.
If a week is a long time in politics, a fortnight after a decisive derby day could feel epochal.
United's Premier League money may have mitigated debt but Wilder, who returned last December with a relegation course long set, is drawing on a coaching toolkit assembled right through the pyramid to reshape and renew after the top-flight trauma.
Though key players like Oli Arblaster - a boyhood Blade still only 20 - Gus Hamer and Anel Ahmedhodzic were retained amid summer interest, bouncing back was never a gimme; a double-figure exodus has prompted a significant rebuild in personnel and system.
Kieffer Moore, Harrison Burrows and Michael Cooper are proving shrewd signings but takeover impasse thwarted the late transfer activity that aimed to add depth. Jesurun Rak-Sakyi and Alfie Gilchrist are talented loanees playing at this level for the first time. Sydie Peck, Andre Brooks and Ryan Oné - the teenager who replaced injured Moore in midweek and scored his first senior goal - have been elevated in importance coming through United's productive academy.
Defeats at Leeds and Middlesbrough reminded that this remains a transitional squad, yet, an instructive 14 games in, United would be top but for a two-point deduction over defaulted transfer payments. Tuesday’s late show at Bristol City, prompting wild celebrations between players and fans, showed that the restoration work has been psychological as well as tactical and the overriding sense is that there is more to come.
Wilder’s return was questioned by some supporters, stung by an angry break-up and sceptical after anomalous spells at Middlesbrough and Watford. But the 57-year-old, reflective and hungry, insisted Sheffield United would be getting "the best of me".
Masterminding another day to remember would add to the mounting supporting evidence.
Up the road, hope springs from relative stability.
If Darren Moore's exit after Wednesday's remarkable play-off triumph in 2023 felt lamentable, the months that followed - Xisco Nunez sacked by October and Chansiri criticising supporters in stream-of-consciousness statements - appeared reckless.
The Owls looked doomed after three points from 13 games last term, before Danny Rohl, a 34-year-old with coaching pedigree at Bayern Munich but no managerial experience achieved "mission impossible" on the final afternoon.
Prizing positioning as well as pressing - they have made more as a team than any other in the division - Rohl has reinvigorated Wednesday, even if they remain erratic performers amid heightened expectation.
After an opening 4-0 win over Plymouth came defeat to Sunderland by the same scoreline. A capitulation against Watford last weekend - five second-half goals shipped in a 6-2 defeat - prompted shock and fury, but was followed by a storming win over Norwich.
Telling has been Rohl's considered response to setbacks in the moment and a recruitment vision that he describes as "clear for the next two windows".
Chansiri, with welcome actions over words, sanctioned summer arrivals into double figures and has tied the young German to a deal until 2027. Long beyond Sunday, putting continued trust in Rohl's process appears key.
Rohl says he has absorbed "feedback" from the streets about the significance of the showdown, but as he prepares for a first Sheffield derby in what will be his 50th game in charge, he is sure to lean on Barry Bannan's experience.
At 34, Bannan may be in his 10th Owls season but he remains instrumental to chance creation, afforded licence by the impressive Southampton loanee Shea Charles, who snuffed out Borja Sainz's threat in midweek.
In the midfield duel, Wilder will hope that Vini Souza can continue the form that has seen United's Kop triumphantly demand he join them in the pub rather than in the stands. Unable to progress the ball and frequently out of position last season, the Brazilian is irrepressible right now, breaking up attacks, muscling aside opponents and recovering possession around the box.
United will need to shift the ball with tempo and utilise Callum O'Hare's movement between the lines; Burrows - with two goals in his last two games - has benefited from space in behind down the left. Wednesday's Josh Windass, with improved attacking numbers of his own playing predominantly from the right, will look to exploit any overly-ambitious forays.
On the right flank, home fans will urge Rak-Sakyi to get the ball and often. The Crystal Palace youngster, with more take-ons and touches in the opposition box than any of his colleagues, remains raw but his direct running and dribbling is terrorising defences. That he could come up against two former Blades in Max Lowe and the resurgent Marvin Johnson makes the match-up more tantalising.
But United may well need to be patient. Rohl has shifted his Wednesday units higher up the pitch, but he is a flexible tactician and a low block looks likelier at Bramall Lane.
Gus Hamer is capable of audacious quality but with Moore doubtful, the towering defensive duo of Harry Souttar and Anel Ahmedhodzic could provide more elementary route to goal; Wednesday have conceded the most goals from set-pieces (9) and corners (six) so far.
A stat that will do little to stave off queasiness is that almost of a third of goals in Wednesday's games this season - for and against - have come in the final 15 minutes.
Don't leave early.
It is one game, just 90 minutes, and yet, in Sheffield of all places, it is anything but.
Watch Sheffield United vs Sheffield Wednesday live on Football and Main Event from 11.30am Sunday, kick-off 12.30pm.