Godwill Kukonki impressed the Portuguese manager in his first week of first-team training and has been rewarded against Ipswich Town.
Amorim, who is just three years older than veteran defender Jonny Evans, has shown his commitment to promoting young talent.
Kobbie Mainoo and Alejandro Garnacho have both become mainstays of the first-team since rising through the ranks under Erik ten Hag.
The Dutchman's successor Amorim may now have found his first academy success at Old Trafford in the form of Kukonki.
The 16-year-old turned heads at Carrington after joining the senior stars in training and is now on the bench against Ipswich.
Read more on Man United
'I love that kid' - Amorim reveals forgotten Man United star is huge part of his plan
'I am different' - Dreamer Amorim delivers box office first Man United press conference
The budding centre-back is one of the tallest players in his age range at a whopping 6ft5, which is an inch taller than Harry Maguire.
His imposing physique, coupled with his versatility to play at left-back for the U18s, has already earned him comparisons to Josko Gvardiol.
Kukonki could solve a problem area for Amorim, who is renowned for using three central defenders in his favoured formation.
Man United signed right-footed defensive pair Leny Yoro and Matthijs de Ligt this summer, but are believed to remain keen on a left-footer.
Most read in Football
Jose Mourinho responds to 'ridiculous' Cristiano Ronaldo rumours but makes him an offer
Ex-Chelsea star misses open goal from eight yards in miss of season contender
Spurs inflict record home defeat on Guardiola's City, Amorim set for first Man United game
Guardiola's 'nightmare' and Cunha prepares for 'interest' - talkSPORT's winners and losers
talkSPORT revealed this month that United are plotting a fresh move for Everton defender Jarrad Branthwaite next summer.
United had two offers for the England international worth up to £50million rejected before the start of this season, but the 22-year-old remains at the top of their wish-list.
However, Kukonki has a natural ability to play with his left which could spare the club having to match Everton's reported £80m price tag.
His secondary role at left-back will also be highly useful to Amorim, considering Luke Shaw and Tyrell Malacia's injury history.
Kukonki has scored one goal and registered an assist in his nine appearances for United's Under-18s so far.
He is yet to make his Premier League 2 debut but has got an assist in his only UEFA Youth League outing from left-back last month.
Kukonki was an unused substitute in the 2-0 win over Newcastle in the Premier League 2.
He did make a brief cameo outing in the National League Cup as United's Under-21s beat Forest Green Rovers 3-2 in October.
Manchester United fans think forgotten man Mason Mount is already impressing Ruben Amorim in training