When: Sunday, May 2, 16:30 BST
How to watch: Sky Sports Main Event
It's hard to believe the turnaround from last season if you're a Liverpool fan.
The Merseysiders finished 33 points ahead of Manchester United as they powered to the title; going into this one, they're 13 points behind their great rivals from down the East Lancs Road.
With five games remaining, United already have a point more than they managed in the 2019/20 campaign.
And they head into Sunday's showdown after thrashing Roma 6-2 at Old Trafford on Thursday night. That gave them a sixth win in seven games and put them virtually through to the final of the Europa League.
What's more, this is a fixture that they dominate. In the last 15 meetings at Old Trafford, it's 10 wins for United, four draws and just a single victory for Liverpool.
Last three meetings:
Man Utd 3-2 Liverpool (January 24, 2021)
A week after they'd played out a 0-0 stalemate in the league at Anfield (see below), this FA Cup clash was a far more entertaining encounter.
Salah levelled just before the hour mark with his second of the game but the hosts struck the decisive blow when second-half substitute Bruno Fernandes blasted home an excellent 78th-minute free-kick to send United through. Both teams had 14 shots overall and six each on target.
Liverpool 0-0 Man Utd (January 17, 2021)
Before they went on a horror run of six straight home losses, Liverpool played out a drab 0-0 draw with United at Anfield.
Given what was to come, the visitors would see this as a missed opportunity and, indeed, Ole Gunnar Solksjaer used that phrase post-match after watching his side carve out the better opportunities.
Liverpool 2-0 Man Utd (January 19, 2020)
Wind back a year from that 0-0 and this was Liverpool in their pomp: steamrollering everyone before them and charging towards the title.
Virgil van Dijk headed them into a 14th-minute lead and, after facing some late United pressure, the Reds wrapped up the victory when Salah coolly slotted home after being sent racing clear by Alisson's long clearance.
That clincher seemed a symbolic moment, sparking joyous scenes as Liverpool's fans really started to believe that this was their year. From here, it just seemed a matter of when not if.
Head-to-head - last 10
Man Utd wins: 2
Liverpool wins: 2
Man Utd scored: 8
Liverpool scored: 10
Liverpool still hoping for top four but time running out
With their final four games against Southampton (h), West Brom (a), Burnley (a) and Crystal Palace (h), Liverpool remain in the hunt for a Champions League spot.
But any slip-up here could just leave them with too high a mountain to climb.
How the Reds must rue their last two matches.
They were on target to beat Leeds at Elland Road before conceding an equaliser in the 87th minute. And it was even later against Newcastle as two more points were spurned after Joe Willock levelled for the visitors five minutes into added time.
Those two matches add to the feeling that this just isn't Liverpool's season. In which case a rare win at Old Trafford seems hard to envisage.
Liverpool's last five results:
Arsenal 0-3 Liverpool (Jota 2, Salah)
Liverpool 2-1 Aston Villa (Salah, Alexander-Arnold)
Liverpool 0-0 Real Madrid
Leeds 1-1 Liverpool (Mane)
Liverpool 1-1 Newcastle (Salah)
Scoreline prediction: Man Utd 2-1 Liverpool
As stated, United have a superb record against Liverpool at Old Trafford and that makes the odds for Sunday's clash seem somewhat baffling.
Liverpool are 6/4 favourites, with United as big as 9/5 at William Hill.
True, the Red Devils have the second leg of their Europa League semi-final to complete but a 6-2 advantage from the first leg suggests a huge part of the job is done.
And do we really think they'd take their eye off this fixture? Solskjaer knows how big it is and a victory would send them off to Italy in great spirits.
Klopp has never won at Old Trafford in six attempts and I don't see that changing.
United are value for the win and a 2-1 scoreline looks worth taking at 10/1.
Best goalscorer bets
Mason Greenwood scored in United's 3-2 FA Cup win over Liverpool in January with a superbly-taken strike.
He also netted in the 6-2 win over Roma and the late goal was his sixth in eight games so the youngster has really found his scoring boots again.
Greenwood came on as a 76th-minute substitute in that European tie and, given his freshness, it increases the chances of Solskjaer unleashing him here.
Liverpool are still conceding goals so Greenwood to score anytime at 15/4 with Unibet looks generous.
For the visitors, Salah remains their only reliable scorer and is available at a best 7/5 with Unibet.