Former Italy goalkeeper Giovanni Galli has claimed Manchester United were scouting Amad Diallo Traore for over a year.
The Red Devils spent €40m to sign the 18-year-old from Atalanta, where he will remain until January.
"I know a scout of Manchester United very well as we usually meet at games. He used to tell me that the club sent him several times to watch the player."
And the 62-year-old added that there was justification for United paying such a large sum for the teenager.
"[The transfer fee] is high, but there is a reason behind it," he said.
"[Diallo] still needs to get a work permit since he has not played with his national team yet.
"The club need to have valid reasons to take him to the UK. One reason is that the player is coming from a top team and with Atalanta [having] been playing international competitions over the last few years, there are no problems to prove it.
"The second reason is the price tag. A €40m signing means he is an important investment for the club.
"If the cost would be €1m or €2m it may have been more difficult to get the work permit. That being said, €40m is still a lot of money."