Chesterfield midfielder Derek Niven is being treated for testicular cancer his club have confirmed.
The 24-year-old underwent surgery on Thursday to remove a tumour and is awaiting further tests.
A club statement read: "Everyone at the club wishes Derek a full recovery and a speedy return to action for the Spireites."
Niven joined the club in December 2003 from Bolton and has gone on to make 199 league appearances, scoring 14 goals.
The Scotsman has made 16 appearances this campaign scoring the one goal.