Not for the first time, three letters dominated this weekend’s Premier League action: VAR.
The mistake that saw Liverpool have a goal wrongly disallowed in their 2-1 loss to Tottenham on Sunday has sparked more debate about the use of the video assistant referee.
The referees’ governing body described it as a “significant human error” – but Liverpool say that explanation is “unacceptable”, claiming “sporting integrity has been undermined”.
BBC Sport looks at the key questions.
The game was goalless when Luis Diaz’s 34th-minute strike was ruled out on the field for offside.
The decision was incorrectly upheld by VAR, with play cleared to continue despite still images showing Tottenham defender Cristian Romero playing Diaz onside.
It is understood the correct procedure was followed for the offside decision but the mistake was down to human error.
Football Association (FA) rules state that after play has restarted, referees can go back to ‘review’ incidents of mistaken identity or a red card for serious incidents such as violent conduct, but not for offside after play has restarted.
Video assistant referee Darren England and his assistant Dan Cook were stood down for their next assigned Premier League games, which is a common occurrence when an error is made.
What do Liverpool want?
Liverpool released a statement on Sunday saying they will “explore the range of options available given the clear need for escalation and resolution”.
The Reds are also unhappy that the game restarted so quickly without sufficient time to intervene. The club have called for a review into what happened “with full transparency”.
Former Manchester United defender and Sky Sports pundit Gary Neville was critical of the statement, calling it a “mistake”.
“Talk of exploring all options (what does that mean!) and sporting integrity are dangerous phrases along with being vague and aggressive,” Neville wrote on X, formerly Twitter.
Could the game be replayed?
It is not clear what options Liverpool are referring to in their statement. There is no precedent in the UK for either a match result to be changed or for a game to be replayed due to a refereeing error.
A 1999 FA Cup tie between Arsenal and Sheffield United was replayed only because Arsenal boss Arsene Wenger offered that olive branch after the winning goal was scored in controversial circumstances.
What about the UAE trip?
VAR officials for the Liverpool match – England, Cook and fourth official Michael Oliver – were also part of an officiating team who took charge of a league game in the United Arab Emirates on Thursday, just 48 hours before Saturday’s fixture.
The Football Association had approved the trip, with the trio arriving in London on Friday to prepare for Saturday’s game.
It is understood that Liverpool also want this looked at as part of PGMOL’s review.
These appointments are done on an FA-to-FA request basis and there are currently no further visits to the UAE or Saudi Arabia scheduled, though this may change.
Is this an issue?
Craig Pawson refereed Panathinaikos v PAOK in the Greek Super League on 3 May, while Andy Madley did two matches in Japan’s J League and Japan’s Kirin Cup match against El Salvador in June.
Both of these visits came after requests from the respective FAs. Oliver also took charge of a Saudi Pro League game in April.
The flight time to the United Arab Emirates from the UK is approximately seven hours, with a time difference of three hours.
BBC Sport’s Dan Roan says: “While the FA and PGMOL both approved the request, and match officials [as well as teams] regularly go overseas for midweek European fixtures, it will raise questions as to whether fatigue from the trip to the Middle East may have played a role in their decision-making.
“The PGMOL believes such foreign assignments enhance the international standing of their officiating, and make the point that referees from other countries do the same.”
Some people believe that allowing officials to work for leagues in countries with connections to Premier League clubs could lead to claims of a conflict of interest.
Nine English top-flight teams have American owners, with a 10th – Everton – having agreed a takeover deal with an American investment firm, while at least three have Middle East owners and another is in Chinese ownership.
What do the referees say?
Ref Support UK, a charity that provides training and support for referees, said: “This past weekend has probably been one of the toughest for top-flight match officials in England.
“Hopefully this will be a turning point for the game and for VAR. There will always be humans involved in the decision-making process in football, and humans, both players and referees, are fallible and will make mistakes. It’s how we learn from these mistakes that will take the game forward.
“Introducing a law change to allow a match official to change a clear error after play has restarted would be a good pace to start.”
President of the Referees’ Association, Paul Field, said: “Players, coaches, managers and match officials don’t deliberately make errors and we will wait for the PGMOL to make a detailed investigation and take whatever operational action they deem appropriate.
“We continue to be concerned about the level of abuse being aimed at match officials and remind people that comments made in the media and by pundits have outcomes at all levels of the game, but notable at grassroots.”
When was VAR brought into football?
Video technology is relatively new to football.
VAR was only introduced to the Premier League at the start of the 2019-20 season, while goalline technology has been in place since 2012.
The Premier League’s guiding principle for VAR is that it should be used for “clear and obvious errors” and “serious missed incidents” in four types of match-changing incidents – goals, penalties, straight red cards and mistaken identity.
Semi-automated offside technology was used at the 2022 World Cup but is not yet in place in the Premier League. PGMOL chief Webb has previously said that its introduction has been discussed.
BBC Sport’s Simon Stone says: “The Premier League could have introduced it at the start of the season but decided the system was not quite right. It remains under review but cannot be introduced mid-season unless 14 or more Premier League clubs voted for it.
“Instead, the Premier League introduced four additional VAR cameras.”
Could VAR rules be changed as a result?
There are strict rules around what can and cannot be used when it comes to VAR, and they are controlled by the international game’s rule makers Ifab.
An ongoing trial of referees confirming VAR rulings to fans in stadiums will continue at the men’s Under-17 World Cup in Indonesia later this year. However, it would require a shift from the present position for them to agree to full conversations between referees and VAR to be made available in real time.
What other VAR controversies have there been?
There have been a number of notable VAR controversies this year.
In February, Brentford’s Ivan Toney equalised at league leaders Arsenal when he nodded in Christian Norgaard’s cross from close range, but Toney and Norgaard both appeared to be offside in the build-up to the goal.
Despite a lengthy review, VAR Lee Mason did not draw the lines to check for offside on Toney’s goal and the decision to award the equaliser stood, with the game finishing 1-1.
Mason left the PGMOL a few days later by mutual consent.
In August, Wolves had a penalty claim against Manchester United turned down by the referee and that decision was upheld by VAR, though the PGMOL later admitted this was a mistake.
The Wolves and Fulham incidents were addressed in the TV programme Match Officials: Mic’d Up, with PGMOL boss Webb.
The new show, introduced for this season, aims to explain refereeing decisions using in-game audio of on-field officials and VAR teams.
What happens next?
Times journalist Henry Winter called for a number of improvements including live broadcasting of VAR decisions, VAR specialists and a new rule allowing an emergency intervention up to 10 seconds after a restart.
BBC Sport’s Simon Stone added: “Some kind of communication around the whole situation is expected and Webb does have it in his power to release the audio to shine a light on exactly what happened if that is decided as the chosen way forward.
“In addition, the latest Premier League appointments will be released at 10:00 BST on Tuesday. Under the circumstances, it would be a major surprise if England or Cook were given games.”
How are video referees used in other sports?
The use of video referees is much more established in other sports.
For example, the television match official (TMO) was introduced in rugby union in 1995 and rugby league in 1996, while cricket umpires have been able to refer some on-field decisions to a TV third umpire since 1992. The Decision Review System (DRS), which allows for player reviews, was introduced in 2008.
Such sports can show replays of incidents and broadcast audio between the officials live on TV and in the stadiums.