Ole Gunnar Solskjaer was keen to strengthen at left-back and a £15.4 million deal to sign Alex Telles from Porto was completed on deadline day.
United had also been linked with Ajax defender Nicolas Tagliafico during the summer.
But according to Fabrizio Romano on the Here We Go podcast, United’s Plan B if they failed to sign Alex Telles was to land Emerson from Chelsea.
It is claimed that United did not make an official approach to Chelsea but the club did hold initial talks with Emerson’s representatives.
Chelsea, who now have three left-backs in their squad following the £50m signing of Ben Chilwell in August, were open to letting Emerson leave and join a club in Serie A on loan.
However, Chelsea were unwilling to strengthen a rival and would not approve a loan deal which would have seen Emerson join Old Trafford.
Romano claims that United were ‘convinced’ by Emerson but were put off by Chelsea’s potential demands to sign the Brazil-born Italy international on a perment deal.
Emerson joined Chelsea for £17.6m from Roma in January 2018 but has been unable to establish a regular role since moving to Stamford Bridge.
Reports claimed this summer that Chelsea were holding out for a £26m fee for the 26-year-old.
‘He is a player we have been tracking for some time and his performances over the past few years are exactly what we are looking for,’ said Solskjaer.
‘He is a fighter and a winner and will add real determination and competition to the squad.
‘Alex has the qualities, both as a player and as a person, that we want here at Manchester United.’