When David Moyes was struggling at West Ham, Amorim was flown in to an interview for the managerial role before the club decided to stick with the Scotsman.
Now it has been revealed why the Hammers decided against the Portuguese, who looks set to be the next United manager as talks continue between the two parties.
The Hammers would have had to pay £8.3m to snap up the Sporting Lisbon coach which was originally the reason why many believed Moyes was favoured by the club.
However, as reported in the Daily Mail, it has now been revealed that the club felt that appointing Amorim would represent a major gamble as he has only managed one top club in his own country so far in his career.
Amorim has coached three different teams in his homeland but despite this experience, there was doubts about him handling the scrutiny of the Premier League.
United are hopeful of getting a deal over the line before they face Chelsea on Sunday, with talks between all parties now underway.