Derby striker Nathan Tyson is set to miss the Rams' next five matches with a groin injury.
Tyson, a summer signing from East Midlands rivals Nottingham Forest, suffered the injury during the first half of last week's pre-season victory over Aston Villa at Pride Park.
He sat out the opening-day win over Birmingham on Saturday and is expected to miss the Championship fixtures against Watford, Blackpool, Doncaster and Burnley, as well as the Carling Cup tie against Shrewsbury on Tuesday.
"People said it must have been a big boost on Wednesday beating Aston Villa but we'd have swapped the win to have Nathan available," said manager Nigel Clough.
"He has had a scan and we think he is going to be out until after the international break in September. He will probably miss the first six games of the season - and we will miss him.
"He has had a couple of groin problems in pre-season but it is unrelated to those. A tackle made on him jarred him a bit. He tried to carry on and it got worse. It's just bad luck."
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