Real Madrid could face disqualification from the Copa del Rey after fielding an ineligible player in their fourth-round win over Cadiz, report Spanish media.
Denis Cheryshev, 24, gave Real the lead but the Russian should have been serving a one-game ban, say reports.
Newspaper AS has published a document showing he received three bookings in the domestic cup competition while on loan at Villarreal last season.
This first-leg tie was the first opportunity he had to serve the ban.
Real boss Rafael Benitez was manager of Valencia when they were disqualified from the Copa del Rey - the Spanish Cup - having played too many non-European Union players in a tie against Novelda in 2001.
Last season Osasuna were kicked out of the tournament for playing an ineligible player after Unai Garcia was selected in the win over Mirandes despite having been sent off the previous season.
Cadiz will have to report the situation to the Spanish Football Federation on Thursday.
The club's Twitter feed, said during the game: "The Board of Directors of @Cadiz-CF will meet at the end of the match."
Cheryshev was taken off moments after half-time as a double from Isco secured victory for the 19-time Copa del Rey winners, with Kike Marquez scoring a late goal for the hosts.
- 1Ballesté López
- 2Márquez Sánchez
- 4Hernández UmpiérrezSubstituted forSánchez Barahonaat 71'minutes
- 5Malagón Rubio
- 3Sánchez MesaSubstituted forMárquez Climentat 45'minutes
- 6Garrido MoraciaBooked at 58mins
- 7Sánchez Ponce
- 10Coronado PláBooked at 53mins
- 11Pavez Muñoz
- 9Cuero LlanoSubstituted forGonzález Güizaat 71'minutes
- 12Sánchez Barahona
- 13Cifuentes Martínez
- 14Márquez Climent
- 15Pérez Quintana
- 16González Güiza
- 3PepeSubstituted forTejero Sacristánat 89'minutes
- 10RodríguezSubstituted forLienhartat 78'minutes
- 20Rodríguez Ruiz
- 21CheryshevSubstituted forKovacicat 46'minutes
- 29Mayoral Moya
- 34Tejero Sacristán
- Ricardo de Burgos Bengoetxea
- Shots on Target