Chesterfield winger Gary Roberts is undergoing tests in an attempt to get to the bottom of his heel problem.
Roberts has been hampered by the injury for the past couple of weeks and the summer signing from Swindon is a doubt for the Spireites ahead of their home game against Southend on Saturday.
"We are still a little bit worried about Gary at the minute in terms of him not training since (the Rochdale game last weekend), and if you don't train during the week then it affects your performance on the Saturday," said Blues boss Paul Cook.
"We are having the problem fully investigated. We will get more results from scans, because what we don't want is players playing while they are injured.
"It isn't fair to the player or the supporters, who judge what a player does out on the pitch. So certainly with Gary we want to make sure that he is 100 fit so that when he goes out on the pitch he can do what we all know he is good at."