Fresh from finishing a lowly eighth last season, Erik ten Hag paid the price for the club's worst ever start to a Premier League campaign with his job, so how can Amorim succeed where everyone else post Sir Alex Ferguson has failed?
talkSPORT takes a look at Amorim's in-tray as he sets about the enormous task of restoring the Red Devils to their former glories.
IMPLEMENT A DEFINED PLAYING STYLE
Even in the aftermath of May's FA Cup final triumph over Manchester City - undoubtedly United's greatest day of the post-Fergie era - the questions marks over Ten Hag's philosophy (or lack of) remained.
The truth is that white knuckle cup ride, which included a barely believable extra-time win over arch-rivals Liverpool and almost being knocked out in the semis by Coventry despite leading 3-0 with 19 minutes of normal time to go, summed up United's inability to dominate games the way they had in their illustrious past.
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Even in the final itself, which many labelled a tactical masterclass, United had a little over 25 per cent possession against the team Ferguson famously branded 'the noisy neighbours'.
As so often under Ten Hag, who was recruited partly because of the possession-based game he was able to deploy so successfully at Ajax, the Red Devils relied on moments of individual brilliance and hitting City on the counter attack as a route to glory.
Ten Hag tried to change that this summer and the early signs were good as United enjoyed greater control and played fewer direct passes, opting instead to build from the back, in their penalty shoot-out defeat against City back at Wembley.
But after losing at Brighton in their second league game, any sign of an identity quickly went out of the window again, with huge gaps appearing in midfield and the opposition allowed to dictate the flow of matches.
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Like Ten Hag, Amorim arrives with a defined high-energy playing style, and part of the reason Liverpool opted against pursuing their interest in him was because they didn't feel his 3-4-3 formation would suit their squad. Unlike Ten Hag, the 39-year-old has to be brave enough to stick with his principles.
CUT THE DEADWOOD
The fact there are players on the United books who have survived three or four managers should be a massive red flag to Amorim.
While offloading under-performing big earners like Marcus Rashford will be very difficult, a much-needed summer clear-out will be helped by the fact that Harry Maguire, Victor Lindelof, Christian Eriksen and Jonny Evans are all out of contract at the end of the season and should all be let go.
Casemiro has enjoyed an upturn in performance level under caretaker-manager Ruud van Nistelrooy, but is hard to envisage the veteran Brazilian being able to meet the rigorous physical demands that Amorim places on his charges.
Luke Shaw conveniently returned to training soon after ten Hag had departed, but cannot be relied upon to stay fit so is another that should be moved on, while there are already big question marks from within the corridors of Carrington over £36.5million summer recruit Joshua Zirkzee being cut out for the Premier League.
Rashford is a fascinating case study; a player who initially excelled under Ten Hag and enjoyed the best scoring season of his career before the relationship deteriorated to such an extent that sources say the pair were barely on speaking terms by the end.
England outcast Rashford is said to be enthused by the prospect of working with Amorim, but recent performances suggest he is a very long way from being back to his best and if that doesn't change quickly then United may have a brutal decision to make with their academy poster boy.
When fully fit Mason Mount looks perfectly suited to playing alongside Bruno Fernandes as one of the two number 10s behind a lone number 9, but he really needs a run of games between now and the end of the season to salvage what has so far been a disastrous move from Chelsea.
talkSPORT has already revealed that the £80m Antony has been told his future is elsewhere and he could depart as early as January, albeit a loan move back to the Dutch league or his native Brazil looks the most likely scenario.
TURN RASMUS HOJLUND INTO GYOKERES '2.0'
There is no better illustration of how far United's star has fallen than the fact that even after Sunday's 3-0 win over Leicester they have still scored only TWELVE goals in ELEVEN Premier League games. That's the same number as Erling Haaland alone and fewer than Wolves and Leicester.
However, it is not like this is a team who struggle to create chances. In fact they have spurned more big opportunities than any of the other 19 clubs.
In contrast Amorim's Sporting team plundered 39 goals in their first 11 league games - all wins - and hit four past Manchester City in the Champions League. He also turned Viktor Gyokeres - deemed surplus to requirements by Brighton - into one of Europe's most sought-after strikers with clubs including Chelsea and Arsenal keen to bring him back to England next summer.
The United hierarchy will hope he can have the same impact on Rasmus Hojlund, who has netted just twice in his 12 appearances this season.
With United another potential suitor for Gyokeres, although their recruitment will be led by sporting director Dan Ashworth and technical director Jason Wilcox and not Amorim himself, the pressure is on Hojlund to start finding the net on a consistent basis.
TARGET THE EUROPA LEAGUE
There may only be four points separating 13th placed United and Chelsea in third but the quality level in the top half of the table has arguably never been so high.
It is almost impossible to see a scenario where leaders Liverpool and champions City, even taking their current wobble into account, don't finish in the top four so the battle for the two, maybe three depending on the success of English teams in Europe, other Champions League places is going to be fierce.
While improving last season's worst ever Premier League finish is one of the main priorities with so many games still to play, winning the Europa League may offer an easier route to a seat back at Europe's top table.
After ending a year-long wait for a European win by beating Greek minnows PAOK 2-0 last week, United have a very winnable set of games coming up at the start of Amorim's tenure and should easily finish in the top eight to go straight into the last 16.
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The new UEFA format also means they do not have to contend with teams dropping down from the Champions League so it is no surprise that United and Tottenham, flaky away from home, are the top two favourites to lift the trophy.
Amorim led Sporting to the quarter finals in 2023, knocking out Arsenal in the round of 16 so knows his way around the competition United last won under his mentor Jose Mourinho seven years ago.