Bordeaux midfielder Toma Basic will not be able to play in the Europa League group stage after the club forgot to include him in their squad list.
Club president Stephane Martin said the 21-year-old had been left out because of "an administrative error".
"He will be able to participate in the Europa League from the round of 32 onwards," Martin said.
Basic signed from Hajduk Split last month and has come off the bench in two Ligue 1 games.
On Wednesday, the club named Brazilian Ricardo Gomes as their new manager to replace Gustavo Poyet after failing to agree a deal with former Arsenal and France forward Thierry Henry.