Neymar's debut for French club Paris Saint-Germain could face further delay as French football authorities are still awaiting clearance for him to play for the Parisian club following his world record $263 million move from Barcelona last week.
France's Ligue 1 organizers, the LFP, told CNN Sport that the Spanish football federation has until Thursday night to send the necessary documents or the Brazilian -- who already missed a league game on Saturday -- will not feature in PSG's Ligue 1 match against Guingamp on Sunday.
An International Transfer Certificate (ITC) is required for all international transfers, says football's governing body FIFA. But the French league has yet to receive this from its Spanish counterparts and so cannot register the Brazilian.
A spokesperson for the LFP said: "The Spanish federation of football has until Thursday night to send the international contract of transfer to the French federation of football, who send it back to the French professional football league, and then Neymar can play with PSG this weekend."
The 25-year-old, who has signed a five-year deal which makes him the highest-paid player in the history of his sport, was unveiled at the Parc des Princes last Friday.
Spanish league officials initially tried to block the deal after PSG triggered the release clause for the 25-year-old's contract, claiming the French club was breaking the Financial Fair Play rules set by UEFA, European football's governing body.
But there could be further stumbling blocks ahead in a transfer which has been far from straightforward.
If the LFP does not receive the certificate by August 18, FIFA would have to intervene.
Even if the certificate is received, Neymar and Barcelona need to confirm their contract has expired. A failure for all parties to reach a mutual agreement would see FIFA rejecting the ITC.
In a statement, a FIFA spokesperson said: "Once [the ITC] has been completed the former association of the player asks the player and his former club to confirm if his contract has expired, if it was ended early or on mutual agreement or whether there is a contractual dispute.
"The ITC can be rejected if the contract between the player and his former club has not expired, or if there is no mutual agreement regarding its early termination."