Derby County manager Nigel Clough says John Brayford is 'playing on one leg' and is concerned by the full-back's ongoing thigh injury.
Brayford recently returned from missing six matches with a torn thigh muscle, but was forced to come off during Saturday's defeat at West Ham United.
The defender had also felt discomfort in the area in the previous week's game against Hull City and Clough is anxious not to worsen the problem.
"John's playing on one leg. His thigh is still sore but he is getting through," said Clough.
"It is a concern because we want him fully fit and having three games in seven days doesn't help."
Derby host Brighton & Hove Albion on Tuesday night and return to London on Friday night to take on Crystal Palace.
Clough hopes Brayford can battle on but he added: "At least having Paul Green fit again gives us an option at right-back."