Inter Milan vice-president Javier Zanetti has lifted the lid on Marcelo Brozovic's row last week.
The midfielder was dumped for victory over Juventus.
“He was unhappy with his substitution in the Europa League and wanted to leave the stadium," the Vice-President told Gr Parlamento on Rai TV.
“It was a gesture that prompted the Croatian exclusion from the Derby d'Italia.
“There are very specific rules in place. First of all, the club must always be respected. Then there's the respect of one's teammates.
“If he wants to continue to build what we're doing with us then he'll always find open doors with us, but it depends on him."