City boss Paul Tisdale told the club's official website: "Adam has been in hospital now for five days.
"He is a big miss because he is a player who is very good at finishing games, so whatever way you use him he is a big asset."
The club have said Stansfield is not expected to return to first team action for at least two weeks.
Tisdale added: "We want all our best players available but the important thing is he gets healthy again before we even think about training and playing."
Source: BBC Sport
Source: BBC Sport