Mainoo signed a new five-year contract this week, pledging his future to his boyhood club until the summer of 2031 as he brushed aside transfer rumours.
The England international has been key to United success this season, especially under interim manager Michael Carrick.
He has started 12 of his 13 games in charge, only missing the defeat to Leeds through injury and as he works his way back into the side he was asked by GQ about the first name he ever had on a replica shirt.
“(Wayne) Rooney. Growing up, he was the guy at United. He was the man, so back then I don't think you'd get anyone else's name on your shirt.”
When asked who he might choose if he were a young fan today, he added that he would go for two of his current teammates.
“Probably Bruno (Fernandes) or Amad (Diallo). When I was younger, I loved that type of play, a tricky winger to play against.
“And Bruno because he's an unbelievable player, what he's done for the club. He's been here for a while now and what he's doing in the season is amazing as well.”
Mainoo has provided three assists in 26 appearances for United this season and he will hope to add more to his tally as he clashes with Liverpool on Sunday alongside both Fernandes and Amad.