Controversy over the selection of Denis Cheryshev marred Real Madrid's 3-1 victory over Cadiz in the Copa del Rey on Wednesday.
Madrid's status in the competition could be under threat after under-fire head coach Rafael Benitez started the Russian, despite him being due to serve a ban for receiving three bookings in last season's competition.
It was Cheryshev who opened the scoring early in the match, before he was replaced almost immediately after half-time as confusion reigned over whether he was allowed to play, while Cadiz officials confirmed they will meet after the match to discuss their next move.
Two goals from Isco in the second half sealed a comfortable first-leg away victory in the round of 32 for Madrid, before Kike Marquez scored a late consolation, but all eyes will now be on the aftermath and any potential verdict against Benitez's men.
Cristiano Ronaldo, Gareth Bale, Karim Benzema, Luka Modric, Toni Kroos, Danilo and Keylor Navas were all rested for Madrid, while Marcelo, Dani Carvajal and Sergio Ramos were all ruled out with injury.
Madrid had the lead within three minutes. A brilliant lofted pass from James Rodriguez found Cheryshev, who beat the hosts' offside trap on the left, took one touch and drove a low left-footed shot into the bottom corner.
Cadiz, who sit third in Segunda Division B, made a decent initial response as Lolo Pla headed wide, before Salvi set up an excellent chance for Wilson Cuero with an impressive run and reverse pass, only for the striker to be denied as Kiko Casilla saved with his legs.
Lolo was narrowly off target with another effort, while James shot just wide at the other end after creating the opportunity for himself with a neat turn in a crowded penalty area.
Lucas Vazquez hit the side netting after a neat one-two with Jese Rodriguez as the visitors reached half-time with a one-goal advantage.
After Cheryshev was substituted within a minute of the restart, Jese and James both had efforts saved early in the second half.
The victory was sealed 25 minutes from time when Isco did well to chest down a long pass from Casemiro and slot a right-footed finish past Pol Balleste.
And Isco got his second and Madrid's third eight minutes later. The playmaker cut inside on to his right foot after collecting James' pinpoint pass and a combination of Balleste's one-handed save and a half-hearted effort from recovering defender Josete on the line failed to keep it out.
Cadiz almost got a goal back when Dani Guiza curled a shot just wide after seizing on a defensive error before they did strike with a consolation on 88 minutes.
Pepe only half-cleared a cross from the right into the path of Marquez, whose bouncing shot beat Casilla as both sides move to awaiting developments on Cheryshev.