The defending champions have now lost each of their last four games in the Premier League, and have remarkably picked up fewer points this calendar year than their bottom-of-the-table hosts.
A year ago to the day of this game, Liverpool were enjoying a 44-match unbeaten league run, a record-equalling 18-match winning streak and sat an unprecedented 22 points clear at the top of the table.
Many were tipping Jurgen Klopp's side as Invincibles back then, but they look as far from invincible as possible right now, and it could be argued that their decline began with their defeat to Watford on February 29, 2020 - in the 12 months before that, the Reds did not lose a single game; in the 12 months since they have lost 10 times.
The real nosedive in form has occurred since the turn of the year, though, with Liverpool losing six of their nine Premier League outings in 2021 - incredibly as many defeats as they had suffered in their previous 100 top-flight games before that.
Four of those defeats have come on the bounce ahead of this game - the only respite coming with a Champions League triumph over RB Leipzig - and another loss on Sunday would make it five top-flight defeats in a row for the first time since 1953.
The fact that you have to go back to the days before Bill Shankly for a run so bad speaks volumes about the trouble Liverpool are in at the moment, and how to halt such a dramatic demise after years of success will be one of the biggest tests Klopp has faced in his managerial career.
The most recent defeat was the most disappointing yet as Liverpool's long unbeaten run in the Merseyside derby came to an end, with Everton winning at Anfield for the first time since 1999 and beating their nearest neighbours home or away for the first time in more than a decade.
Last weekend's result means that Liverpool have now lost four successive home league games for only the second time in their history and the first time since 1923, and away from home things have not been too much better this term.
The champions have only won three of their last 11 league games on the road, and all four of their away victories this season have come in London; Klopp's men have taken just four points from a possible 21 in away games outside the capital.
Despite that, Liverpool have not lost back-to-back away league games for more than four years, and regardless of their recent form they will be favourites heading into this one as they look to get their season back on track.
A return to winning ways needs to come sooner rather than later with Liverpool now languishing in sixth place and the gap to the top four now standing at five points, while both Everton and Aston Villa are within striking distance behind them with games in hand.
The statistics certainly look bleak for Liverpool, who have already conceded more goals this season than they did throughout the whole of 2019-20, while their tally of 40 points from 25 games is the third-worst of any defending champion in Premier League history.
The Reds need only look to Sunday's hosts for evidence that things could be much worse, though, and such statistics will not evoke sympathy from the Sheffield United fans enduring one of the worst seasons in top-flight history.
Last weekend's 1-0 defeat to fellow relegation zone dwellers Fulham means that they have lost 20 of their 25 league games this season - the fastest any team has ever reached that unwanted milestone in the English top flight.
Chris Wilder's side also have the worst attacking record in the league this season with just 15 goals from 25 games, in addition to the fewest clean sheets - just one.
That clean sheet came in a 1-0 triumph over Newcastle United last month - their first win of the season and the beginning of a run of three wins in five games which gave them a glimmer of survival hope after picking up only two points from their opening 17 outings.
However, that hope has been extinguished by back-to-back defeats at West Ham United and Fulham which have left them 14 points from safety with only 13 games remaining.
Indeed, rather than survival the main target for the Blades right now will be to avoid going down as the Premier League's worst ever team - a dubious title currently held by the Derby County class of 2007-08.
Sheffield United have already reached their 11-point tally and so need just one more point to avoid that fate, but given their form throughout the course of the season so far, they will not take achieving that for granted.
Even accounting for Liverpool's form, not many Sheffield United supporters will be expecting anything from Sunday's game, with the Blades having lost their last seven matches against the reigning top-flight champions.
Liverpool have also won their last four Premier League meetings with Sheffield United, although another victory on Sunday would see them win back-to-back home top-flight games against the Blades for the first time since 1921.
Sheffield United Premier League form: WLWLLL
Sheffield United form (all competitions): LWLWLL
Liverpool Premier League form: WWLLLL
Liverpool form (all competitions): WLLLWL
Liverpool's relentless centre-back injury troubles continued last weekend as Jordan Henderson limped off, and the skipper has since undergone surgery on his groin which could keep him out for up to eight weeks.
Klopp is hopeful of having his captain back at some point before the end of the season, but he joins an infirmary inundated with influential figures alongside the likes of Virgil van Dijk, Joe Gomez, Joel Matip, James Milner and Fabinho.
Milner and Fabinho should return to training ahead of Sunday's game but are not expected to be involved, while Diogo Jota will be assessed ahead of the game having also been back on the grass this week.
Klopp must also decide whether to start goalkeeper Alisson Becker, whose father tragically drowned in Brazil this week. The shot-stopper will be given the option to sit out if he wants.
Ozan Kabak and Nat Phillips ended the Merseyside derby as Liverpool's 18th different centre-back pairing of the season, and they could both feature from the start on Sunday despite January arrival Ben Davies also pushing for a start.
For all of Liverpool's poor form as a team, Mohamed Salah's continued goalscoring has provided a positive and he arrives at Bramall Lane with 16 goals in his last 17 away games across all competitions - as many as he had netted in his previous 51 on the road for the Reds.
Like Liverpool, Sheffield United have seen their centre-back options in particular decimated by injuries this season.
John Egan, Jack O'Connell, Chris Basham and former Liverpool man Jack Robinson will all miss Sunday's game through injury, while Wilder's defensive options are further limited by Jayden Bogle's absence.
Bogle will miss at least a couple of weeks after the challenge which controversially did not end up in a penalty for the Blades last weekend, while Basham also picked up his injury in that defeat to Fulham.
Sheffield United possible starting lineup:
Ramsdale; Ampadu, Jagielka, Bryan; Baldock, Lundstram, Norwood, Fleck, Stevens; McGoldrick, Sharp
Liverpool possible starting lineup:
Alisson; Alexander-Arnold, Kabak, Phillips, Robertson; Thiago, Wijnaldum, Jones; Salah, Firmino, Mane
We say: Sheffield United 1-2 Liverpool
The success of 2019-20 for these two sides feels like a long time ago now, and both clubs come into this match having been decimated by injury in a key area of the field this season.
Both are in poor form and the fact that Sheffield United would sit above Liverpool in a 2021 Premier League table may give the hosts optimism that they can pile more misery on their visitors this weekend.
However, recent defeats mean that Sheffield United's focus is realistically now on Championship football next season, whereas Liverpool know that they need wins quickly to salvage their own season, and we can see the champions returning to winning ways here.
Watch the Sports Mole Football Shorts prediction for this game below: