Since its first use in England in January, the benefits of VAR have been a hot topic of debate. Will it work? Is it even worth it? Or do we just need to be more patient?
VAR's benefits are difficult to quantify, but the IFAB's (International Football Association Board) eye-opening study of nearly 1,000 games provides hope.
Here, as part of Support The Ref week on Sky Sports, we've trawled through the data and answered the biggest concerns…
Q: We've only used it in a handful of games in England, but it seems to have caused a lot of problems. What about around the world?
The study, by IFAB and KU Leuven, looked at the 972 competitive matches to have used VAR across over 20 national associations since March 2016.
Fans, players and managers have rightly been concerned by how much VAR disrupts the flow of play.
This was no more evident than at Tottenham's victory over Rochdale in February, a freezing cold evening at Wembley with several VAR interventions.
The stats show, however, that VAR reviews only come into play roughly one in every three games.
- 69.1 per cent (672 games) had no VAR review, while only 5.5 per cent had more than one review.
- 57.4 per cent of checks were for penalty incidents and goals
- 42.1 per cent were for red card incidents
- Negligible for mistaken identity situations
Wait, what's the difference between a VAR 'review' and VAR 'check?
This is important. Most 'checks' take place 'in the background' and have no impact on the game (or the referee), but in some cases the referee has to delay the restart of the game for the VAR to complete a 'check'. So when the crowd are jeering the referee for taking time over an incident, it is often the VAR deliberating.
Checks are signalled by a finger to the ear and a hand in the air, while reviews are indicated by making the sign of a TV screen.
Once the VAR has informed the referee what the 'check' shows the referee will then decide whether there should be a review and whether that review will be based solely on information from the VARs (VAR-only review) or involve the referee going to look at the replays pitch-side (On-field review).
But just how long do these 'reviews' and 'checks' take?
The median time taken for all incidents is 20 seconds, and the majority of checks take place while play continues or during 'normal' stoppages like goal celebration or when the ball out of play.
VAR-only reviews take a median time of 35 seconds, while on-field reviews take around 68 seconds.
But here's the thing: the average time lost to VAR is 55 seconds, a small dent on game time in comparison with:
- Free-kicks - 8m 51s
- Throw-ins - 7m 2s
- Goal-kicks - 5m 46s
- Corners - 3m 57s
- Subs - 2m 57s
OK, great. But just how accurate are the VAR interventions? So many of these decisions are still subjective!
Before VAR comes into use, the initial refereeing accuracy across the games in the study is at 93 per cent.
But that level of accuracy after VAR use is boosted to 98.8 per cent. Yes, this isn't perfect, but that isn't the goal.
Referees' chief Mike Riley says: "The biggest challenge is understanding that this isn't about making the game 100 per cent perfect.
"It is to address and reduce clear and obvious errors. We don't want this to sanitise the game or for it to be stopping every two minutes while everyone stands around and gets frustrated."
Initially (before VAR), there is on average one clear and obvious error every three matches. VAR corrected this in 18 out of 19 matches, and in nine per cent of matches, VAR had a decisive impact on the outcome (win, lose, draw).
So, the benefits are there. But how do we make the most of it?
To fans, players, managers, and even officials, VAR is in its infancy. This isn't a simple vanishing spray; it should be a huge step in the right direction and a two-way process is needed.
Those on the playing side, including fans, must offer their patience, and officials must identify failures, improve, and most importantly, not impact on the viewing and attending experience, something Spurs boss Mauricio Pochettino is worried about.
Practice should make perfect, and former referee chief Keith Hackett agrees.
"It is evident that the more officials get used to the system the better they become. The Premier League might want to look carefully at the results posted by IFAB before raising the white flag to say 'not for us'."
Follow the debate all week on SSN and on our digital platforms at www.skysports.com/supporttheref