Derby manager Nigel Clough admits John Brayford's thigh injury is a cause for concern.
Brayford, an ever-present last season having not missed a minute of action in the Rams' 48 fixtures, has started the last two games after a torn thigh muscle kept him out for six matches.
However, he felt discomfort in his thigh in the home defeat to Hull and came off after 77 minutes of the defeat at West Ham on Saturday. The Hammers led 3-1 at the time and Clough did not want Brayford to make his injury worse.
"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 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."