Cadiz have announced they will report Real Madrid to the Spanish Football Federation (RFEF) over their selection of the ineligible Denis Cheryshev in the Copa del Rey.
The capital club, who won 3-1 in Cadiz, could be thrown out of the competition as Russia international Cheryshev was picked despite failing to serve a suspension for receiving three yellow cards with former club Villarreal last season.
The winger opened the scoring in the third minute of Real's fourth round first leg tie at Estadio Ramon de Carranza but was withdrawn from the action moments after half-time, when Real had realised their error, with head coach Rafael Benitez saying they wanted to "show good faith".
Nevertheless the president of third tier Cadiz, Manuel Vizcaino, has revealed the club's board has opted to report Real for the transgression.
He told cadizcf.com: " This situation required a speedy decision because there was no time to speculate. The board has met and decided to report Real Madrid for fielding an ineligible player, out of respect for our fans and the club.
"We decided to do this with a heavy heart, but it is our firm decision. We do this not without a sense of pain, because we are friendly with the club (Real).
"We read the report, evaluated the situation and weighed up our decision. I think we've acted responsibly.
"I spoke with people from Real Madrid during the match and nobody said anything about it. We've looked at the rules and made a decision accordingly, but it was a tough one to make.
"Real Madrid are a great club, admired all over Spain, and by me."
Last season Osasuna were kicked out of the tournament for playing an ineligible player while Benitez was in charge of Valencia when they were disqualified from the Copa del Rey having played too many non-EU players in a tie in 2001.
Benitez told Real's official website: "Clearly, the club did not know anything. We weren't told by Villarreal or the RFEF.
"We knew nothing and (when we found out), we have substituted the player to show good faith."
Real director Emilio Butragueno said in quotes published in Marca: "We knew nothing of the situation.
"We had no notice from the RFEF or from Villarreal. Cheryshev, who was a Villarreal player at the time, had no knowledge.
"We will await developments."
Cheryshev said he did not receive notification from his former club that he would be banned.
He told his current club's website, realmadrid.com: " I did not receive any notification from Villarreal to inform me that I had been banned from playing in the Copa del Rey."