Emilio Butragueno and Rafa Benitez insist Real Madrid did not know about Denis Cheryshev's suspension which should have ruled him out of the Copa del Rey win over Cadiz.
The winger scored the opening goal but it was later discovered he was ineligible to play, and Madrid could get disqualified as a result.
Butragueno, director of institutional relations, blamed Villarreal, with whom Cheryshev was booked three times in the cup last season, incurring a one game ban, for not passing on the message.
"This week has not been easy and this night has been even more complicated," he said on Canal+.
"The situation is this. We didn't receive any notification from the federation about the banned players, nor from Villarreal, who is the club with whom Cheryshev received the card. And Cheryshev didn't know about the sanction.
"It will be the competition judge who determines what happens. For our part there was no bad will, as all the world knows, but there was a misunderstanding as we received no notification."
Coach Benitez said in his post-match press conference: "The club knew nothing and nor did Cheryshev. Villarreal hadn't informed us and for this nobody knew anything.
"We found out at half-time and for this, I insist, we substituted him to show our good faith. We played a great game in difficult circumstances. We won and I'm satisfied with the players' work."