The report states, the 28-year-old's handful of caps for Argentina could leave Manchester United open to scrutiny when applying for a work permit for the transfer.
However, now the player has been selected for the World Cup squad, Manchester United can add the weight of his inclusion to the case of his transfer.
Now he has been selected for the 23-man squad, Louis van Gaal can go all out to sign the talented Argentine in preparation for next seasons' title push.
Nevertheless, a transfer of this complexity is always likely to bring up questions, so we look to answer them as best we can.
Who is Enzo Perez?
The Benfica number 35 was effectively the replacement, although he was already there, for Nemanja Matic when he left for Chelsea in January.
The Argentinian is a central midfielder by trade, but can also fill in the right-wing position to a high standard when needed.
Nevertheless, it is the central midfield role which has caught the eye of Manchester United and Louis van Gaal would clearly have plans to play him in his favoured position.
Why is the work permit an issue?
The 28-year-old Argentinian, despite his quality, only has six-caps for Argentina in a five year span.
The FA is said to endorse a certificate of sponsorship for a player if he has played 75% of competitive games for a FIFA ranked top 70 nation over the past two years. Failure to meet this requirement will see an application rejected, unless it can be proven a player was unavailable for selection due to injury.
Although Perez falls well short of the 'said' requirements, Manchester United could appeal against the legislation which states: A club may then appeal if the first application is rejected. An appeals panel will then convene to establish whether, in their view, the player's transfer would be of benefit to the game in the relevant country.
A case Manchester United could combat strongly, if he is to make the Argentina World Cup squad.
Are Manchester United the only team interested?
Manchester United are expected to face stiff competition for the Benfica star's signature as La Liga giants Valencia are also reportedly circling the talent.
Experienced Valencia defender Joao Perieira has already talked up the Argentine ahead of a move to the Spanish club. So, if Manchester United are serious about landing their man, then they may need to act fast.