Madrid - Cadiz says it has filed an objection to Real Madrid fielding an ineligible player in their Copa del Rey match.
Madrid faces disqualification from the cup by the federation's competition committee for fielding Denis Cheryshev, who carried over a one-game suspension from last season for accumulation of yellow cards while playing on loan for Villarreal.
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The competition committee is expected to give its ruling on Friday.
Madrid won its opening match of the tournament corresponding to the first leg of round of 32 on Wednesday.
Cheryshev scored Madrid's first goal of the 3-1 victory before coach Rafa Benitez substituted him early in the second half.
In September, the federation disqualified Osasuna from the Copa del Rey for fielding an ineligible player who carried over a suspension from the previous season.