Real Madrid face Cup expulsion for ineligible lineup

Russian international Denis Cheryshev opened the scoring in Andalusia, but shouldn't have been on the field as he was due to serve a one-game ban in the competition after picking up three yellow cards whilst on loan at Villarreal last season.

Cheryshev was replaced a minute into the second-half by Mateo Kovacic.

Cadiz president Manuel Vizcaino insisted his club would present their case to the football authorities if Madrid are found to have broken the rules.

"I will do what the law says and what can be done in the best interests of Cadiz," he told Radio Marca.

Television station Canal Plus reported that Borja Mayoral, who was named on the bench by Madrid coach Rafael Benitez, could also be ineligible under the competition's rules having been sent-off in the final of junior Copa del Rey last season.

Second division side Osasuna were thrown out of the competition earlier this season for fielding an ineligible player in their second round tie against Mirandes.

The administrative error is the latest blow for Madrid after a disastrous couple of weeks that has seen the 10-time European champions fall six points behind La Liga leaders Barcelona after being hammered 4-0 at home by Barca 11 days ago.