Gamez is said to have initially told his fellow officials that Ronaldo was sent off for raising his hand to Gurpegi but has since changed his story.
Madrid are understood to be angry with the change in reasoning and are expected to appeal the red card. They have until Wednesday morning to make their appeal official.
Immediately after Ronaldo clashed with Gurpegi he was also involved in an incident with Iturraspe, with the Athletic player shown a yellow card for his part.
Madrid’s appeal is thought to rest on an error in the referee’s report and the perceived double-standard in sending off Ronaldo but only booking Iturraspe.
The club will also argue that the gesture Ronaldo has been accused of making as he left the pitch was not directed to the fourth official, who it is claimed was not even looking in Ronaldo’s direction.
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