FC Barcelona could be in some hot water, similar to Bafana Bafana, following Thursday's win over Osasuna in LALIGA.
The Catalans defeated Osasuna 3-0 in a rescheduled league meeting on Thursday night, with Hansi Flick's charges moving three points clear at the top of the table.
Inigo Martinez is the player that could cost Barcelona three points having returned from injury.
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Martinez picked up an injury against Atletico Madrid before the international and pulled out of the Spain squad for the UEFA Nations quarter-final against the Netherlands.
FIFA regulation states that any player who is injured and cannot take part in international fixtures is not allowed in the five days after the last international game of that window.
Osasuna have now laid an official complaint with the Competition Committee of the Royal Spanish Football Federation.
"Club Atlético Osasuna has filed an appeal with the Competition Committee of the Royal Spanish Football Federation (RFEF), claiming that FC Barcelona fielded an ineligible player yesterday at Lluís Companys Stadium," the statement said.
"The club argues that defender Iñigo Martínez's participation violated Article 5 of Annex I of FIFA's Regulations on the Status and Transfer of Players. The regulation states that any player who withdraws from their national team squad due to medical reasons - or leaves camp for the same reason - cannot play for their club within five days of the end of the international period.
