Their first match in five years without Chris Wilder prowling on the touchline ended in their biggest defeat of the season. Leicester City were very good in inflicting a 5-0 defeat but the Blades were inept, embarrassing once the roof caved in during the final half-hour.
Wilder's side specialised in plucky defeats this season, just lacking decisive quality at either end of the field. At the King Power Stadium they were as far off as the league table suggests they should be, further than the scoreline indicated.
There was a sloppiness about the Blades right from the kick-off, Oliver Norwood letting John Lundstram's pass squirm under his boot. It was already clear this was going to be a long afternoon for them.
Inside the first 10 minutes Ethan Ampadu hit an attempted square pass to the fit-again Chris Basham comfortably out of play, Basham gave the ball away looking to release Oliver Burke down the inside-right channel, Lundstram did well to chase back and tackle Ayoze Perez only to give it straight back and Billy Sharp's reverse pass was a long way short of the midfielder.
Despite the vast majority of the play behind at the opposite end, Leicester goalkeeper Kasper Schmeichel completed more first-half passes than anyone in pale pink.
There was plenty of energy, as Lundstram's run back had shown, George Baldock doing well to get in front of Timothy Castagne and Basham making a big tackle on Kelechi Iheanacho, but not much else. Leicester, by contrast moved the ball sharply.
It took 13 minutes for them to carve out a really good chance, Aaron Ramsdale – one of the “bad” signings which led to Wilder's departure but late-blooming in recent weeks – doing brilliantly to touch Perez's glanced header from a Castagne cross onto the post.
He saved again from Jamie Vardy when the boyhood Wednesdayite caught Bryan in possession in the area. It became a bit of a theme, the centre-back doing well twice in a matter of minutes after the half-hour doing well to win the ball then immediately being tackled. To his credit, he made sure neither incident came to anything but it showed the Blades had still not sharpened up.
As Heckingbottom watched intently from the edge of his technical area, much quieter than Wilder, with his new assistant, the masked Jason Tindall, making notes in the director's box ahead of his first day today as chief executive Stephen Bettis made mental ones, it just seemed like a question of when the Foxes would take the lead.
Ampadu made a good save with his legs to spare Ramsdale having to deal with a fierce Youri Tielemans shot after 36 minutes but when the Belgian played Vardy in behind Basham four minutes later the striker produced a brilliant cross and Iheanacho peeled off the back of Bryan to tap it in.
Whatever Heckingbottom said at the interval, the game restarted in the same vein, just with Marc Albrighton on to add quality and energy to the hosts.
Bryan made a terrific challenge on Vardy and Basham produced a brilliant header off the line from him but the first was needed because Fleck had once more given the ball away, and blue-shirted players were queuing up to score from the second.
Ramsdale saved when Iheanacho played Vardy through, and Teielemans hit a shot at him but the damn burst again in the 64th-minute, and the visitors quickly went from plucky triers to shambolic.
Norwood failed to pick out the recently-introduced Lys Mousset from a free-kick and Leicester only got it as far away as Baldock but he dwelt on the ball on the touchline and in the blink of an eye, Perez had scored.
It was the first of four goals in 16 minutes.
The third was much like the first, the same excellent combination of Tielemans, Vardy and Iheanacho.
Norwood did well to throw himself in the way of a training-ground corner to Perez but less than a minute later Leicester were able to repeat, no one close enough to the forward, who shot wide.
Easy passes from Wesley Fofana to Wilfried Ndidi to Iheanacho allowed him to score his hat-trick and Amapdu turned in a Vardy cross for the fifth.
Leicester wasted more chances in the final 10 minutes, Iliman Ndiaye on a hiding to nothing when he came off the bench in the 78th minute. This is a ship sinking rapidly.
Leicester City: Schmeichel; Fofana, Evans, Soyuncu; Ricardo (Albrighton 46), Ndidi, Tielemans, Castagne; Perez (Leshabela 81), Iheanacho; Vardy.
Unused substitutes: Ward, Amartey, Choudhury, Mendy, Fuchs, Thomas, Daley-Campbell.
Sheffield United: Ramsdale; Basham, Ampadu, Bryan; Baldock, Lundstram, Norwood (Ndiaye 78), Fleck, Stevens; Burke (Mousset 63), Sharp.
Unused substitutes: McBurnie, Lowe, Jagielka, Foderingham, Bogle, Osborn, Brewster.
Referee: P Bankes (Merseyside).
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