Mainoo's future at United remains clouded despite the dismissal of Ruben Amorim. The midfielder had found himself sidelined by his former manager, which saw Mainoo preparing to leave in January.
While a change of manager has now occurred, with Michael Carrick stepping in this week, the England international still has concerns over his status as new contract talks remain at deadlock.
But Giggs says Mainoo should tough it out, telling BetSelect: "As a footballer, you want to play. But I would have more patience because he is only 20, and it is difficult to play centre midfield for Man United.
"It's like a striker. You don't see many really young strikers playing for Man United because it is difficult. But yeah, we all feel that he should be getting more minutes, but he needs to be patient.
"He's still young, he's still learning the game. And when he does get his chance, he needs to take it. So I'd like to see him stay."