United expect Eriksen to be ruled out until late April but there remains hope he might be able to play again this season.
The club said in a statement on Tuesday: “Christian Eriksen is expected to be out of action for an extended period because of an ankle injury sustained in our FA Cup victory over Reading on Saturday.
“While investigations are continuing, initial assessments indicate that Eriksen is likely to be out until late April or early May.
“However, there is hope that Christian can return in time to play a role in the final stages of the season.”
Eriksen’s injury is a blow to manager Erik ten Hag, who is already without a midfielder Donny van de Beek with the midfielder ruled out until the summer with a knee injury.