It was a mixed start for the new boss at Old Trafford in their 1-1 draw with Ipswich at Portman Road.
Marcus Rashford fired his side into an early lead, but despite this, the Red Devils still looked lacklustre in the middle through Christian Eriksen and Casemiro.
Eriksen, 32, and Casemiro, 32, started in the middle, with Diogo Dalot as a left wing-back and Amad Diallo as a right wing-back either side.
"I'm not sure if this group of players are good enough and Amorim will know that" Manchester football journalist Jamie Jackson told talkSPORT's Inside Devils YouTube show.
Jackson then suggested that the new boss needs to be ruthless in tweaking things when required. "Does he not have it in him to tweak it when needed?" he asked.
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Amorim has been an advocate for the 3-4-3 system, with talkSPORT reporter Angelina Kelly saying the boss would 'die on the hill' of his preferred system.
Jackson offered some curt advice, suggesting the trio of Eriksen, Casemiro and Dalot 'need to go in the long run'.
Co-host Ryon Scott-Douglas said the likes of Eriksen and Casemiro need to be 'press-resistant', but due to their age, this has become more difficult for the pair.
Other more experienced players in the side, such as 36-year-old Jonny Evans, as well as Casemiro, will also struggle under Amorim's new system is dampened, given the fact they have both played much deeper roles throughout their careers.
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"If Amorim's any good, he'll make those three and the team - generally a top six side - are pushing for top four this season," Jackson explained on the YouTube show.
Mason Mount and Amad Diallo, though, are two players 'perfect' for the the new system, according to the show's host, Flex.
talkSPORT reporter Angelina Kelly suggested a different pairing in midfield: "Besides Manuel Ugarte and Kobbie Mainoo as the midfield two behind a front three, who else do you rely on?"
Mainoo has been sidelined for a number of games after suffering a muscle injury in the 0-0 draw with Aston Villa in October, but was an unused substitute in the 1-1 draw with Ipswich Town last weekend.
Kelly suggested Atalanta's Brazilian defensive midfielder, Ederson, who has scored twice and assisted once in 13 Serie A games this season so far.
Despite Rashford's early goal, Kieran McKenna's inspired Ipswich Town - who also played a 3-4-3 formation - fought back with Omari Hutchinson's wonderful strike to leave Amorim with just a point from his first match at the helm.
The midfield will be vital to Amorim's new side but it is notoriously an area Man United have struggled with in the last few seasons, lacking pace and creativity from the centre.
England youngster Kobbie Mainoo has shown signs of his prowess in the centre of the park as a calm and composed presence for his side during what was a difficult campaign last season, but injuries have plagued his start to this campaign.
Eriksen joined Man United in 2022 from Brentford and has since made 86 appearances, scoring seven goals and assisting 16 in his time there.
His experience was paramount to United's squad, having played 296 Premier League games across stints at Man United, Brentford and Tottenham, but he now lacks intensity and mobility in the middle.
Similarly, Casemiro brought a wealth of experience to ten Hag's United at the time. The Brazilian has won five Champions Leagues, three La Liga titles, three Super Cups and three Club World Cups.
He helped Man United win the FA Cup last season, securing a valuable piece of silverware over rivals Man City.
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Under interim boss Ruud van Nistelrooy, Casemiro looked in fine form, but during the Ipswich game he managed less than 71% passing accuracy and was not able to close down opposition attackers.
Eriksen's contract with the club expires next summer, whilst Casemiro is tied until June 2026, although the club may look to cash-in on the veteran midfielder sooner.