When the two English giants first played just three weeks into the 2022/23 season, it looked as if United were in grave danger of a disastrous year while Liverpool had started a bit slower but were by no means out of the title race.
The Reds had drawn their opening two games 2-2 against Fulham and 1-1 against Crystal Palace (as well as recording a superb 3-1 win against Manchester City in the Community Shield), while United had been beaten 2-1 by Brighton and thrashed 4-0 at the hands of Brentford.
Pressure had immediately mounted on Erik Ten Hag and his side, with his players clearly not cut out for the possession style of play that they had attempted in the opening fixtures.
Liverpool, on the other hand, were heavy favourites and the general consensus before the match was just how many goals they would score rather than whether or not they could beat their archrivals.
However, United came out swinging and claimed an invaluable 2-1 win that can now be looked at as a huge turning point for their season - even if only three games had been played.
The paths either side have gone down since that result couldn't be more different, with very few supporters predicting where it would leave them before Sunday's reverse fixture.
Liverpool's plight
The situation didn't seem too bad on Merseyside following their shock defeat, with the Reds bouncing back in style with a 9-0 win against Bournemouth in their following game.
Another impressive result followed when a late Fabio Carvalho winner saw Liverpool beat Newcastle United 2-1, but a 0-0 draw to rivals Everton and a 4-1 dismantling by Napoli left a sour taste in fans' mouths.
Liverpool would, however, record impressive wins against Manchester City, Tottenham Hotspur, Ajax, Rangers and in the reverse fixture against Napoli.
Barring shock losses to Leeds and Nottingham Forest, the Reds were sixth by the time the World Cup came round.
Disappointing, but not a disaster.
Things really started to change following the resumption of domestic football at the end of December 2022.
Despite returning with two wins against Leicester City and Aston Villa, Jurgen Klopp's side would begin to slide down the table.
Brentford made easy work of them with a 3-1 win, Brighton took it a step further with a 3-0 victory before Wolves inflicted more damage with a 3-0 thrashing of their own.
The inconsistency in Liverpool's results has been the real issue - seeing them move as low as tenth in the table.
Picking up results against Everton, Newcastle and Wolves (a couple of weeks on from their initial loss) has seen them move back up to sixth, but the sour mood around Anfield reflects a poor campaign so far.
The Reds were also knocked out of the Carabao Cup (3-2 vs City), FA Cup (2-1 vs Brighton) and are all-but out of the Champions League after suffering a heavy 5-2 defeat against Real Madrid.
When you compare this to their previous season - where they were two games away from winning the quadruple - it makes for utterly disappointing viewing for the majority of supporters.
A result against United on Sunday could act as a platform for a late top four push, but that in itself marks just how far the Reds have fallen since their 2-1 defeat at Old Trafford.
United's success
In contrast, that win for United has seen them go from strength to strength in the games that followed.
The Red Devils have lost just four games in all competitions and drawn another five - winning 29.
They even claimed their first trophy in six years along the way when they beat Newcastle 2-0 in the Carabao Cup final, and have qualified for the Europa League round of 16 after beating Barcelona 4-3 over two legs.
An FA Cup quarter-final tie against Fulham also awaits, leaving United finely poised to complete a quadruple of their own if they can make up some ground in the league.
Ten Hag's side are 11 points behind Arsenal so it would take a mammoth effort and some good fortune, although they do have a game in hand on the Gunners and their neighbours City.
A huge difference between United and Liverpool has been the performances of individual players.
The likes of Marcus Rashford, Casemiro, Lisandro Martinez and Luke Shaw have all excelled over the last few months and contributed to a major shift in momentum.
Rashford in particular has excelled, contributing to 34 goals in all competitions.
Liverpool, on the other hand, have had plenty of players crumble under the pressure and look well below their expected standard.
Darwin Nunez and Cody Gakpo have had promising moments but largely under-delivered, Trent Alexander-Arnold and Andy Robertson haven't hit their usual heights and the majority of their midfielders have been ineffective when called upon.
Going into Sunday's fixture, it seems like there will only be one winner, but it's impossible to rule anything out in high-pressure games like this.
It could be an uncomfortable watch for those on Merseyside if United catch Liverpool on another one of their bad days - but there's every chance that the Reds show up and spoil the party for their rivals.
