FIFA has rejected Leicester's attempts to register midfielder Adrien Silva after the club missed the deadline by 14 seconds.
The Foxes signed the midfielder from Sporting Lisbon for £22million but finalised parts of the deal near the end of the summer transfer window on 31 August.
Silva's registration was not completed in time with football's governing body meaning that if their ruling is upheld he is ineligible until January. Leicester have submitted an appeal against the decision.
A spokesman told the BBC: 'We are working with Adrien and Sporting Clube de Portugal to overcome some issues relating to the player's registration and exploring all options to find a resolution.