VAR, or the video assistant referee, could be the defining factor in this year’s tournament, as the World Cup 2018 kicks off in Moscow today.
32 nations from around the world will head to Russia to take the first steps on their road to World Cup glory, with VAR entering the competition for the first time.
VAR technology has the capability to radically change the way football games are refereed, with controversial or tight decisions being reviewed and scrutinised by independent referees elsewhere via video link.
VAR has proven to be a controversial inclusion to football, with some thinking the technology makes games fairer, while others criticise the technologies inconsistencies as well as complaining that it takes much of the fun out of football and its controversial moments.
Many referees will be using VAR in a professional setting for the first time and fans are predicting the technology to have a crucial impact on the tournament.
What is VAR and how does it work?
VAR is a simple piece of technology that adds an extra official to the game to review incidents after the fact to see if the on-pitch referee made the correct decision.
Similar to that of video referees in Rugby, or the Hawk Cam in Tennis, match officials can request an external referee to review the footage of a particular incident to judge if any further action should be taken.
During the World Cup 2018, 13 officials will be available as video assistant referees, basing in Moscow to review matches across the country as they happen.
Oddly enough, VAR referees will be dressed in full referee-match kits, despite being nowhere near any of the stadiums.
GETTYWorld Cup 2018: Will the World Cup be using VAR tech? What is VAR and how does it work?
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Officials will have access to a huge array of camera angles during each game, with one VAR referee being assisted by three other officials.
During a game, the VAR referee can immediately communicate to the match official if they believe further action needs to be taken on a particular incident, whether that is a handball appeal for a penalty, a red-card offence or a ball teetering across the goal line.
The VAR is only available as an advisor, and cannot make direct decisions for the referee, who can opt to choose whatever course he wishes, even if that goes directly against VAR advice.
You will know when VAR is being called for when the match official stops the game to makes a box-like TV gesture, heading over to the TV review station to watch the footage through again.
FIFA has stipulated that players cannot make the VAR gesture themselves in protest or to influence the referee or suffer a booking.
The technology available to VAR referees allows them to review live footage in real-time with access to dozens of on-pitch cameras as well as a slow-motion video replay.
They will have a constant, live link to all match officials during each game, allowing for open communication throughout the match.
GETTYVAR officials will wear full kit during games
GETTYVAR officials will be able to advise on any event during a game
Why is VAR so controversial?
It took a long time for VAR to be introduced. And that was partly because many people fear it could ruin the flow and feel of the game.
Critics suggest that referees flagging up decisions using VAR – and then taking time to review footage and make their decision – could cause disruptions in play. And they also suggest that it will take away the important nuance that is part of refereeing, butting into matches to decide on any incident that relies on shades of grey.
Fifa president Gianni Infantino says the system has been a "great success", but that work is needed on "the details" such as the speed of decisions.
"Without the VAR, we would have had a different tournament and it would have been a little less fair," he added.
"Thanks to VAR we have achieved a great thing. Those big mistakes will not happen any longer.
"It will always be the referee who decides and there will always be discussions, but big mistakes will be corrected and that is a great achievement after it was asked for so many years."
Whatever the impact VAR has on the World Cup 2018, it is sure to play a big role in how fans remember the global tournament in Russia.
England football team face their first World Cup game against Tunisia on June 18. Gareth Southgate will be hoping VAR will not impede his teams progress through the tournament.