Timm Klose is in Switzerland to visit a specialist over his knee injury, to cap a gloomy fitness bulletin from Daniel Farke ahead of Birmingham City's televised Championship visit on Friday night.
Klose could face up to two months out if he requires surgery, after failing to respond to treatment that included an injection prior to last week's Championship draw at West Brom.
Alex Tettey is also out of the next three games with a re-occurence of the groin problem suffered at Brentford on New Year's Day.
'A setback for Timm in the middle of the week,' said Farke. 'He felt pain in his knee. It is a complicated injury, known more as a 'runner's knee' where there is a problem with the friction. He feels pain and went to London to get a course of injections. Right now he is in Switzerland to see a specialist there.
'There is a possibility he needs an operation which would rule him out for six weeks. We want to try and do it in a conservative way, to find some other solutions. We hope we can have him back sooner but he will miss tomorrow and Sheffield. Without doubt a big leader in our defence.
'Bad news with Alex. A muscle injury with his abductor. He felt some pain again after the West Brom game. We scanned it and he is out for three weks. That means Birmingham, Sheffield and Leeds and hopefully back for Ipswich.
'Moritz Leitner is out and still not back in team training. We hope to get him back next week but it seems like he will just join us after Sheffield United. To have these leaders not available is not easy.'
Marco Stiepermann (quad) has been passed fit for the Blues' visit and Farke reported no fresh injury concerns with those on duty at The Hawthorns,
The City head coach is weighing up whether the likes of Louis Thompson or Carlton Morris feature on Friday afternoon in a scheduled development run out at Colney.
Ben Marshall departed on loan to Millwall on Wednesday but Ivo Pinto's proposed move to Turkey appears to have stalled. Pinto is back in the UK while talks continue but will not be involved for the Canaries until his future is resolved.
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