Real coach Jose Mourinho took off the Brazilian attacker in the 87th minute of Tuesday night's game against the Nerazzurri. Alvaro Carreras was supposed to replace him, but the change did not happen straight away.
With referee Michael Oliver judging Vinicius to be leaving the pitch too slowly, clearly trying to run down the clock with Los Blancos 2-1 up, Carreras was not allowed on immediately.
That left Madrid a man short for a spell and they nearly paid for it. Inter looked to use the extra man and, after working the ball down the left, Henrikh Mkhitaryan got his shot away. Real goalkeeper Thibaut Courtois just about dealt with the former Dortmund player's effort.
Only after Los Blancos cleared for a corner, bringing a stoppage in play, was Carreras allowed to come on. By that point, more than a minute had passed since Vini Junior's substitution, with the 23-year-old only then standing at the touchline.
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What new rule was applied to Vinicius Junior?
Referees have had the option since the World Cup to delay substitutions if the player going off takes unnecessarily too much time to get back to the bench.
Because Vini Jr. took well over the maximum 10 seconds to reach the touchline, applauding towards the stand on his way off while whistles could be heard at times, referee Oliver chose to apply the new rule strictly.
The incident did not affect the final result. After goals from Kylian Mbappe and Federico Valverde, Madrid edged their Champions League opener 2-1. Inter's only reply came through Carlos Augusto.