Ole Gunnar Solskjaer will begin his interim spell as Red Devils manager against the club he suffered relegation with during his only previous managerial stint in the English leagues.
Not many column inches will be dedicated to Cardiff in the buildup to this match following the seismic events at Old Trafford this week, but that will suit the Bluebirds just fine.
While the rest of the football world was digesting the news that Mourinho had been sacked - even if it had had an air of inevitability around it for some time - Cardiff fans may have been more focused on the man taking over the United hotseat until the end of the season.
Solskjaer lasted just eight months in charge of Cardiff in 2014, during which time he led them to relegation from the top flight - finishing bottom of the table - and then suffered a poor start to the next Championship campaign.
In fairness to the Norwegian, Cardiff were never expected to stay in the Premier League when he arrived, and the Bluebirds have had to battle against similarly dismissive odds this time around.
However, despite being installed as comfortable favourites to suffer an immediate return to the Championship, Cardiff approach the halfway point of the season sitting two places and two points above the relegation zone.
There is still a long way to go, of course, and 14 points from 17 games is still not a record to shout about, but Neil Warnock nonetheless deserves huge credit for so far defying almost everyone's pre-season predictions.
It is their home form which has kept Cardiff in the race for survival, with 13 of their 14 points having been accrued in front of their own fans, and the Bluebirds welcome United to South Wales having won four of their last five outings on home turf - as many as they had managed in their previous 22 top-flight home games.
That includes on ongoing run of three home wins on the bounce, and another one against their former boss on Saturday would see them make it four in a row for the first time since January 1961.
Home and away, the Bluebirds have now won three of their last six games - a vast improvement of their run of just one win and nine defeats in their opening 12 outings of the campaign.
Two attributes are usually apparent in teams who successfully beat the drop against the odds - good home form and plenty of character. So far Cardiff have shown both, with nine of their 14 points having come from losing positions this season - a tally only Arsenal can beat.
Recent Premier League form: WLWLWL
It is hard to know where to start when it comes to Manchester United's problems.
Barely a week went by when Mourinho was not falling out with his players, the board, the press or had suffered a poor result, and the toxic atmosphere around the club finally proved too much for the hierarchy earlier this week.
Mourinho's sacking sent shockwaves around world football without actually being that shocking; a 3-1 defeat away to Liverpool proving to be the final straw as the gulf in class between the two sides was embarrassingly laid bare at the home of United's most bitter rivals.
The loss left United 19 points off the leaders - they are closer to bottom-of-the-table Fulham - and perhaps more importantly 11 points adrift of the Champions League places, a gap only one point smaller than the one separating them from Saturday's relegation-threatened hosts.
There are plenty of other damning statistics which could be used to showcase how far United's star has fallen; during Mourinho's reign they won 176 points - fewer than Manchester City, Tottenham Hotspur, Chelsea and Liverpool over the same period - while their tally of 26 points after 17 games of this top-flight season is their lowest since 1990-91.
At the same stage of last season United were 12 points better off, but perhaps the most startling difference between this term and 2017-18 comes in the goals conceded column, where the Red Devils have already let in more this season (29) than they did throughout the whole of the previous campaign (28).
Indeed, only Fulham - who are yet to keep a single clean sheet this season - have prevented the opposition from scoring on fewer occasions than United, which is a particularly woeful record considering they boast a goalkeeper widely regarded as the best in the world.
There are plenty of problems for Solskjaer to address, then - much like when Guus Hiddink steadied Chelsea's ship after Mourinho's 2015 sacking - but there is a vast difference in managerial experience between Solskjaer and Hiddink.
It is a huge job to hand someone whose only previous spells as manager have come at Molde and Cardiff, although first and foremost he should help to get the fans - who still chant his name from his playing days - back onside.
Solskjaer is also a figure who knows the club's values well having won 11 trophies in 11 years as a player and then gone on to be the reserve team coach at United.
As much as the board and fans will be hoping that Solskjaer's appointment galvanises the team, it may actually be that Mourinho's exit has an even greater effect on a group of incredibly talented players that looked shorn of confidence under the previous boss.
A visit to Cardiff is not as easy a start as it might appear at first glance, though, particularly given their home form and the fact that United have picked up only one point from four away games since their memorable win at Juventus last month.
The Red Devils also have an alarming recent record against promoted sides, having lost their last three Premier League away games against teams to have come up from the Championship - as many as they had suffered in their previous 36 such matches.
Recent Premier League form: LDDDWL
Recent form (all competitions): WDDWLL
One of the biggest benefactors of Mourinho's departure could be Paul Pogba, who should now be free to unleash his World Cup-winning quality on the Premier League.
The club-record signing has only started three Premier League games since October and was left on the bench as United slumped to their loss at Anfield last time out, but the new era should see him return to the side.
Pogba is not the only one who will be hoping for a new lease of life after Mourinho's exit, with Antonio Valencia, Fred and Anthony Martial all likely to be pushing for a starting role for this match.
Romelu Lukaku could also be absent having reportedly been given compassionate leave this week.
Cardiff possible starting lineup:
Etheridge; Ecuele Manga, Morrison, Bamba, Peltier; Hoilett, Camarasa, Gunnarsson, Arter, Murphy; Reid
Man Utd possible starting lineup:
De Gea; Valencia, Bailly, Lindelof, Shaw; Fred, Matic, Pogba; Lingard, Rashford, Martial
Head To Head
Not since 1960 have Cardiff beaten Manchester United, with the Red Devils having won five and drawn two of the seven meetings since that Division One clash.
Indeed, that is Cardiff's only triumph in the last 12 editions of this fixture, with the most recent of those coming during Cardiff's last stint in the Premier League.
United won 2-0 the last time these two sides met - courtesy of goals from Robin van Persie and Ashley Young - but their most recent visit to the Cardiff City Stadium saw the Bluebirds pull off a memorable 2-2 draw with a last-gasp equaliser.
We say: Cardiff 1-2 Man Utd
This is such a difficult game to predict, with Cardiff having hit form at home but United likely to be revitalised by their change of manager. Despite the difference in calibre between the two sides it really is one which could go either way, but we're backing Solskjaer to get off to a winning start against his former club.