Grant Hanley will miss at least six weeks of Norwich City's season with a quad injury.
Daniel Farke confirmed the news on Friday afternoon at Colney ahead of the weekend's Championship home game against promotion-chasing Middlesbrough.
Hanley went for scans over the international break and has been ruled out until November at the earliest.
Ivo Pinto will also miss the Teessiders' clash with a hamstring issue.
'Grant will be out for at least the next six weeks. Could be eight. He has a rare injury with his quadricep,' said Farke.
'I had never heard this before. He had the problem for several weeks but was able to play and train and was brilliant at Ipswich. We used this international break to scan him and the doctors find this injury. It is called 'degloving' in his quad. The muscle fibres have a tendency to go away from each other.
'The risk is too big to let him play because he might need an operation then. He could be out for months so we have given him a special injection therapy and if everything works he is back after the international break. Maybe six or eight games. We felt after pre-season he was coming into his rhythm.
'It's bad news that Grant is out but the young lads can step up now. I trust all of the lads. Christoph (Zimmermann) has shown he is capable to perform.
'The same goes with Ben (Godfrey). He is developing really well and did well at Cardiff and was solid against Ipswich
'We have a core group of leaders. Timm (Klose), Alex (Tettey), Ivo and Christoph - they can all wear the armband so I'm not concerned who is captain in Grant's absence.
'Ivo has a slight problem with his hamstring. We don't take any risks. He had a big, big injury in this area in pre-season so not for this weekend. With it being a similar injury to the one he had in pre-season we will not take any chances.'
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Mario Vrancic is fit for duty this weekend after a pelvic problem but Farke reiterated Nelson Oliveira is still not under consideration after failing to earn a move in the summer transfer window.
'Mario's available and back in the mix,' said Farke. 'He trained pretty good. His last game was at the end of April. It's not so easy to come into the game rhythm. But he's back and available for Saturday.
'After a long period of being out it always makes sense to think about the under-23s and a game but on the other hand Mario is an experienced player. He could handle the Championship. Maybe an option for 20 or 30 minutes in the battle.'
Louis Thompson and Kenny McLean are both closing in on returns to action from hamstring and ankle injuries respectively before the end of the month but are unavailable for the Teessiders' test.
'After the Ipswich game I was pretty concerned about Louis. It didn't look so good,' said Farke. 'He seems to have recovered better than I expected. At the end of the month he will be back in training and available pretty quickly.
'The same with Kenny. Perhaps even the end of next week or the week after they can re-join team training. I am looking forward to having them back. They are crucial lads.'
Farke confirmed he had no fresh concerns over his international contingent.
Matt Jarvis remains a longer term absentee.
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