Referee Deniz Aytekin was in charge as Barcelona faced Paris Saint-Germain in their last-16 second leg last March, and since this controversial officiating performance, a series of mistakes have followed, which has led to questions being asked over whether the UEFA Champions League needs to introduce video assistant refereeing (VAR).
FIFA have continued to test such a system, with March's international friendly match between Spain and France seeing VAR used for the first time, and successfully as well.
The Russian World Cup in 2018 will be when the football world may see video referees in full operation, as this is the plan according to FIFA president Gianni Infantino.
UEFA have improved their ways by adding hawk eye, but will wait to see if the World Cup is a success or not first before the Champions League will see it implemented fully.
Here are some of the most controversial moments from this season`s Champions League:
Barcelona vs PSG: Javier Mashcerano's foul in the box on Di Maria
A clear penalty should have been awarded, as the Argentine defender takes out his fellow countryman, whilst the PSG attacker is clear on goal, with the scoreline at 3-1 to Barcelona.
Barcelona vs PSG: Penalty decision after foul on Luis Suarez
There was much controversy regarding the penalty decision awarded for a foul on Suarez. With the help of VAR this could have been resolved much quicker and could have taken the pressure off the referee.
Atletico Madrid vs Leicester City: Foul on Griezmann outside the box
Replays showed that a penalty awarded for Atletico was actually a foul which started outside the area but continued inside. This lead to a goal in the 1-0 victory over the Foxes.
Borussia Dortmund vs Monaco: Kylian Mbappe clearly offside for goal
Monaco striker Mbappe put the French side 1-0 up, but again with television cameras you could clearly see that he was yards offside.
Real Madrid vs Bayern Munich: Arturo Vidal's second yellow card awarded, but tackle seemed fair
Vidal was shown a second yellow and sent off, but the Chilean clearly won the ball in a tackle on Madrid's Marco Asensio.
Real Madrid vs Bayern Munich: Cristiano Ronaldo`s goal was offside
Going into extra-time, Ronaldo's equalizing goal against the Germans showed he was a yard offside, as Los Blancos went on to qualify for the semi-finals.
The Spanish Federation is in full election process, and one of the candidates Angel Maria Villar, believes VAR should become part of the process in the future of football, and he does not rule out the idea of trials for next season.
His first idea, which MARCA have reported on in the past, is to place goal line referees in Spanish competitions. Jorge Perez is another candidate that as is 100% in favour of VAR, with it quickly becoming a major election issue.
