Boss Kevin Blackwell said: "Eirik's situation is very worrying. We're keeping our fingers crossed it is not as serious as we fear. With his recent problems, it could be trouble."
The Norway international missed most of last season due to knee and thigh injuries.
United will be hoping that the injury is not one that would take Bakke out of the season for a long time, as their recent cull of players means fewer to choose from next season.