Chesterfield defender Jamie Lowry could miss the rest of the season with glandular fever.
Blood tests confirmed his illness as glandular fever after he failed to respond to an initial course of antibiotics, and he has now been advised to undertake at least a four-week period of complete rest.
He will then embark upon a two-month battle to regain full fitness, but Chesterfield boss Roy McFarland insists he will not be rushed back.
"We are really disappointed for Jamie because he has made a real impact on the squad," said McFarland.
"He recently got the chance for some early first-team experience and did a decent job for us in some key matches.
"The important thing now is to ensure Jamie makes a full recovery and, as we do not intend to rush things, it may mean he could be out for the rest of the season."
Teenager Reuben Wiggins-Thomas, meanwhile, has signed his first professional contract after being offered the chance to remain with Chesterfield until the end of the season.
"Reuben has worked hard in training and deserves a chance to earn himself a longer-term contract," praised McFarland.