Leny Yoro is understood to have spoken to other former Manchester United players while he mulled over whether to join the club.
United had an initial EUR62million fee accepted by Lille amid competition from Real Madrid and Yoro took around a week to make his decision.
It is understood the 18-year-old spoke to other esteemed ex-United players, who were asked to keep their discussions with Yoro confidential.
Former United defender Rio Ferdinand publicly confirmed that he had advised Yoro, who speaks impressive English, to move to United.
"Two weeks ago, he called me," Yoro told club media. "We spoke for ten minutes about Man United, so he helped me a lot to make my choice.
"He mainly spoke about the club and what it's like. That this is a historic club with a big story, and if I go there I need to fight for the club, to be ready, because this is the biggest club in the world.
"It was really good to speak about this."
Ferdinand contacted Cristiano Ronaldo when he appeared to be bound for Manchester City in 2021 and urged him to rejoin United.
Yoro made his first appearance for United in their 2-0 friendly win against Rangers in Edinburgh on Saturday.
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