Los Blancos had lost the first leg 2-1 in Madrid and found themselves 4-2 down on aggregate, yet Zidane chose to bring on Lucas Vazquez, Luka Jovic and Fede Valverde in the 83rd minute, leaving Vinicius watching on from the stands.
"I find it hard to understand why he didn't play after what he's achieved this season, being one of the best wingers in LaLiga," Rivaldo told Betfair when asked about Vinicius.
"And besides, there wasn't any news about injuries or anything like that.
"I'm convinced that, if he had played, he would have been a headache for [Pep] Guardiola.
"But he sat out the entire 90 minutes of the game, in such an important tie.
"Surely only Zidane and the boy know what happened and what they talked about before the game, but from the outside it can only be understood as a strange decision.
"If there was nothing personal or an injury, it's a controversial decision by Zidane and a difficult moment for Vinicius, who would have loved to take part in such an important Champions League match."
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