The Club is therefore unable to complete the registration of Adrien’s transfer from Sporting. As a result, he will be ineligible for selection until January, when the transfer window – and its associated registration period – re-opens.

A Leicester City spokesman said: “We cannot hide our disappointment or that of the player at the short-term consequences of the decision.

“We maintain, and have made strong representations to FIFA’s Players’ Status Committee, that all parties involved in Adrien’s transfer fulfilled their obligations, consistent with FIFA regulations and within the required timeframe. The Club is reserving its position in relation to whether it will decide to appeal the decision to the Court of Arbitration for Sport.

“The Club and its staff will continue to work with Adrien to hopefully minimise the impact that missing a substantial period of the season may have on the player, while continuing to prepare the squad for the games ahead.”