Barcelona are the subject of an official complaint from La Liga side Elche following what they believe to be an "improper selection" of midfielder Gavi on Saturday.
La Liga leaders Barca ran out 4-0 winners, with Robert Lewandowski bagging a brace and Ansu Fati and Ferran Torres also getting in on the act.
Gavi registered an assist in an impressive performance away from home and was whistled by the home supporters at the Estadio Martinez Valero when he was substituted for Franck Kessie in the 68th minute.
But Elche are furious and with three minutes to spare before a deadline, launched a complaint over the fielding of the 18-year-old.
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They are going off RFEF's (the Royal Spanish Football Federation) rule from article 141 stating players cannot "play again in the same season with a canceled license".
Their case is in relation to the registration of Gavi's contract at the Nou Camp. Over six months ago, Gavi put pen to paper on a deal until until 2026, with a €1 billion release clause inserted and the arrangement including him inheriting the iconic No.6 shirt previously worn by his manager Xavi Hernandez.
La Liga did not approve the registration because of salary regulations but Barca then sought a legal ruling which saw it overturned.
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However, when the matter went to court, La Liga won the battle and an appeal from Barca was rejected - essentially meaning Gavi has returned to his youth contract.
He is no longer listed as a first-team player on the club's website and Elche believe he is effectively an ineligible player.
If the ruling goes against the Blaugrana, COPE reports they could risk being stripped of points and unable to play Gavi for the rest of the campaign.
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However, SPORT say Barca are "very calm" over the situation as they are adamant approval from La Liga and the RFEF was confirmed on Friday prior to the game.
Still, the predicament is less than ideal for the Catalans as they must trim their wage bill so that the contract can be registered and valid by July 1.
Gavi could therefore be available on a free transfer in the summer and will have a queue of potential suitors.
Josh Lawless