Jewell said: "Scharner has had an operation and is going to be out for six to eight weeks, which is a blow for us.
"We haven't the biggest squad in the world, and now we've quite a few injuries."
Jewell is also hoping to add to the signing of Swedish defender Andreas Granqvist, who signed from on loan from Helsingborgs on Thursday, stating another midfielder and at least one striker remain on his January shopping list.