Mount was forced off in the first-half of the win at Manchester City last week.
TalkSPORT says Mount's leg injury is set to see him sidelined for several months. It's suggested the midfielder won't be seen again until March.
United manager Ruben Amorim stated on Tuesday: "I don't know the exact date, but it's going to be for long. And that’s it, it's part of football and you continue."
"What I can do is to help Mase, to teach him how to play our game when he's recovering," he explained.
"To try to use that time for him to think about different things. I think the worst part is that we don't have time to train like we should do, when you are recovering from a lot of injuries.
"With Mason Mount, we are going to help him. It is really hard for a player to be out for so long and is trying really hard, the same for me. If they try really hard, we will help them until the end."