Wolves goalkeeper Matt Murray faces a spell on the sidelines as he requires surgery on a knee problem.
The 26-year-old will go under the knife later this week, after suffering pain during training in preparation for the new season.
Manager Mick McCarthy told the club's official website: "We are hoping the arthroscopy shows that he has just nicked his cartilage.
"But until he has the surgery - probably on Thursday - and we've got the results, we won't know how long he is going to be out of action.
"Beyond saying that it will be more than three weeks, we just don't know.
"Matt had hoped it was just going to be a repeat of last season when he injured himself in the Aston Villa friendly, but recovered immediately and went on to play almost all of the season. But that's not the case.
"Wayne Hennessey has been fantastic, but he's the only fit keeper we have now, so we got to look for somebody else."