United completed a €41 million (£37.2m) deal to sign the 18-year-old from Atalanta on deadline day but he will remain with the Serie A club until January.
Diallo, who was born in the Ivory Coast, only made his first-team breakthrough at Atalanta last season and has played just 24 minutes across three substitute appearances for the senior side.
However, his impressive performances at youth level in Italy have been enough to persuade United to make their move.
According to Fabrizio Romano on the Here We Go podcast, United’s hierarchy are ‘convinced’ Diallo is one of the best players in the world in his age category and believe they have signed a rising star.
It’s claimed that prior to completing his move to Old Trafford, Diallo shared a FaceTime conversation with Solskjaer and was highly praised by the United manager.
Solskjaer is said to have told Diallo that he is an important part of United’s future and they are not signing him with a view to immediately send him out on loan.
The United manager also stressed to Diallo that he will need time to adjust to life in England but is convinced he’s ready to make the step up with United.
‘You must ask Atalanta about Diallo. We had the agreement and then the negotiation with Manchester United started and they sold him,’ Parma’s director Alessandro Lucarelli told Sky Sports Italia this week.
‘We covered ourselves with other players and we will make up for it, but he would have been useful.’