Video Assistant Referee causes controversy every week in the Premier League, but how are decisions made, and are they correct?
After each weekend we take a look at the major incidents, to examine and explain the process both in terms of VAR protocol and the Laws of the Game.
In this week's VAR Review: Should Liverpool have been awarded a late penalty against Manchester City? Did the VAR have any grounds to advise Arsenal's Kai Havertz should have been sent off? And how did Brighton's Jakub Moder escape a red card?
What happened: Liverpool won a corner in the 98th minute when the loose ball bounced between Jérémy Doku and Liverpool's Alexis Mac Allister inside the area. The Manchester City forward raised a foot to the ball, with Mac Allister going down from the contact. There appeared to be no claims for a penalty from the Liverpool players, with referee Michael Oliver allowing playing to continue.
VAR decision: No penalty.
VAR review: Mac Allister leans into the ball as Doku attempts to hook it away. The ball touches the body of the Liverpool player first before Doku gets his foot to it, with contact then on the opponent's chest. There are clear grounds for this to be a penalty. A high foot (above the waist) with contact is usually seen as a direct free kick, or a penalty if inside the area. Indeed, if this were in a European league there wouldn't even be a discussion about the VAR intervention.
But this is the Premier League, which wants a higher-intensity game and for VAR interventions to be reserved for only the clearest of errors. That has led to missed VAR interventions far outnumbering wrong ones this season, but the league would no doubt prefer the weight of any errors to be in that direction.
A key factor is Oliver's clear, unobstructed view. If he has seen the high boot, the touch on the ball and on Mac Allister, and has judged minimal contact with the boot not to be enough for a spot kick, then there's not really anywhere for the VAR to go for a review when there's such a high bar.
The VAR, Stuart Attwell, made a lot of Doku getting his foot to the ball (repeatedly saying "plays the ball" and that attempting to win the ball was "reasonable") while believing the collision was then unavoidable. Yet Doku getting that touch doesn't give him free rein to make a high challenge, just as it wouldn't with any challenge. Indeed, contact after a high boot should be an easier decision to give.
"This situation, in all positions on the pitch, is 100 percent a foul," Liverpool boss Jurgen Klopp added after the game. "It's 100 percent a foul and a yellow card."
Yet challenges made inside the area are judged to a higher threshold. To say "it's a foul anywhere else on the pitch" has merit, but that doesn't change the fact that the game isn't refereed that way because a penalty is a greater punishment than a free kick. Think of it as the burden of proof; inside the area a referee believes he must be even more certain of his decision as a goal-scoring chance is the result.
"Isn't it [VAR] there for just making the right decision and not thinking how high a bar you have to overcome to find the right decision?" Klopp said. Yet in a game of subjective opinions there often isn't a "right" decision. Many will rightly believe this should be a penalty. But at the same time many ex-players, including former Liverpool defender Jamie Carragher, can rightly believe the VAR was right to not get involved. For one group a VAR intervention is getting the correct decision, for the other it would be re-refereeing a situation where Oliver had a clear view.
With this system of VAR there are always going to be situations where fans of one club, and many neutral observers too, believe there should be a VAR intervention. Perhaps the highest-profile example this season was Newcastle United's winning goal against Arsenal, with Gunners' fans adamant that the VAR should have disallowed it -- yet it was not an error.
It might be a situation where the Premier League's Independent Key Match Incident Panel views that a penalty is the correct decision on the field, but not enough for VAR. Understandably, that's difficult for supporters to get their heads around, but it explains why ex-referees and players can also believe that it's a penalty but not a VAR error.
There have been a few examples involving Liverpool this season. Andy Robertson's challenge on Brentford's Ivan Toney last month was unanimously voted by the panel to be a penalty on the field (coincidentally, the referee was also Oliver), yet it voted 4-1 against a VAR intervention.
Liverpool have also had such judgements go in their favour. The panel said the referee was wrong to give Dominik Szoboszlai a penalty against Bournemouth, and Diogo Jota shouldn't have been awarded a spot kick against Newcastle -- but neither were sufficiently wrong to be overturned on review.
What happened: Manchester City took the lead in the 23rd minute when Kevin De Bruyne whipped a corner to the near post, which was helped in by John Stones. However, was there blocking by Nathan Aké that allowed Stones the space to score?
VAR decision: Goal stands.
VAR review: Liverpool fans asked how this could possibly be different from Virgil van Dijk's second-half goal in the Carabao Cup final, which was ruled out after Wataru Endo had blocked off Chelsea's Levi Colwill.
Van Dijk's goal was ruled out for an offside offence by Endo, not a foul.
No player can be offside from any restart when the ball has been out of play (corner, goal kick, throw-in), so Ake hasn't committed any such offence.
Ake cannot be offside, which leaves only a foul. While the Manchester City player is in contact with Mac Allister, there's no chance that the VAR will get involved in such a situation.
What happened: Liverpool were awarded a penalty in the 47th minute when Darwin Núñez raced to close down a back pass, got to the ball first and was brought down by goalkeeper Éderson. Referee Oliver pointed to the spot and booked the Manchester City player.
VAR decision: No red card.
VAR review: Ederson's challenge was late, but double jeopardy means that a foul inside the area with an attempt to play the ball cannot be seen as a red card.
That said, it's likely that Ederson was booked for a reckless challenge, rather than for denying an obvious goal-scoring opportunity (DOGSO) because of the run of the ball.
The only grounds for a red card would be if Oliver believed Ederson's challenge had excessive force or endangered the safety of an opponent, or if the goalkeeper's only intention was to take out Nunez in a DOGSO situation.
When Van Dijk was sent off against Newcastle the foul was outside the area, so not covered by the double jeopardy exemption.
What happened: Jakub Moder was booked by referee Michael Salisbury in the 67th minute after a strong challenge on Neco Williams. The VAR checked for a possible red card.
VAR decision: No red card.
VAR review: Recently we've seen yellow cards with contact above the ankle rightly not upgraded through VAR, as far as how the game is officiated in England anyway, such as Harry Maguire's tackle on Sasa Lukic and Moisés Caicedo on Ryan Gravenberch in the Carabao Cup final.
In both those cases the offending player was stepping into a challenge. This incident shows when the line is crossed and it's hard to understand how the VAR, Craig Pawson, failed to tell the referee he had made a mistake.
Moder sprints into the challenge, leaves the floor and makes contact with the Nottingham Forest player above the boot with force.
There's absolutely no doubt this is a red card, the sixth of the season not picked up by the VAR.
It's Pawson's only Premier League VAR error of the season, and what's more surprising is that he was on VAR duty for Ben Mee's red card against Aston Villa, which came in similar circumstances. But he was also on duty for the incorrect VAR intervention in the FA Cup, which saw Everton's Dominic Calvert-Lewin sent off at Crystal Palace.
Nottingham Forest have now had three missed VAR interventions go against them in the past month, the other two being penalties not awarded against Newcastle United and West Ham United.
What happened: West Ham United won a throw-in in the 97th minute. It was launched deep into the area by Michail Antonio, and as Burnley's Sander Berge attempted to head away at the near post the ball appeared to strike his arm. Referee Darren England immediately indicated no penalty, with the decision checked by the VAR, Andy Madley.
VAR decision: No penalty.
VAR review: David Moyes said after the game: "The boy heads it and his two arms are in front of his head. I don't know if he can head it anywhere else, so he heads it onto his arms and now we're saying that's OK."
The West Ham manager has perfectly described the exemption in the handball law. If a player deliberately plays the ball, either by kicking it or heading it, and it hits their own arm -- even if outstretched away from the body -- there is no penalty.
The logic is that a defender cannot be gaining any advantage if they stop their own play of the ball with their arm.
The VAR was correct not to get involved, and if it had been given by the referee the decision should have been overturned.
Moyes added: "Maybe it's quite a good tactic, you head the ball against your hands."
Yet if the defender was judged to have deliberately handled the ball in this way to control it, then it would be a penalty.
What happened: Arsenal wanted a penalty in the 58th minute. From a corner, Gabriel appeared to be pulled to the ground by Mathias Jorgensen but the on-field officials allowed play to restart with a goal kick.
VAR decision: No penalty.
VAR review: From first view it seemed as though Jorgensen had thrown the Arsenal player to the ground. However, the players were holding onto each other's shirts and there will be no VAR intervention when the offence is simultaneous.
What happened: Four minutes later Arsenal had a stronger penalty claim. Martin Ødegaard chipped a cross into the area and Leandro Trossard went down under pressure from Mads Roerslev. Goalkeeper Mark Flekken punched the ball away with Arsenal players and fans demanding a penalty, while Brentford complained about the actions of Trossard. Referee Rob Jones played allowed play to continue.
VAR decision: No penalty.
VAR review: Roerslev had an arm on the shoulder of the Arsenal player, so the VAR (Paul Tierney) has to evaluate whether that act was a foul on Trossard, or whether the Arsenal player embellished the impact to try to win a spot kick.
The Brentford player is extremely fortunate and takes a huge risk but, as we've seen with other such situations throughout the season, if the attacking player goes to ground theatrically then the VAR is unlikely to advise the referee that he has made an error.
What happened: Ødegaard fed the ball to Kai Havertz in the 65th minute, with the forward going down looking for a penalty under a challenge from Nathan Collins. The ball went out for a goal kick and the referee wasn't interested in a penalty -- but was there a dive by Havertz?
VAR decision: No penalty.
VAR review: Havertz was already on a yellow card, and was very lucky to escape a second booking. While Collins put his right foot out, it's not close to the Arsenal player. There was a small amount of thigh-on-thigh contact, which is probably why Havertz escaped a booking. The referee will also see the ball move to the right, so from his position he cannot be sure it's a dive.
The VAR cannot tell the referee he has missed a yellow card. There are two ways a VAR intervention can lead to a booking: if the referee is sent to the monitor to give a penalty, rejects that review and decides the attacker has dived; or if an awarded penalty is overturned at the screen for a dive.
What happened: Alejandro Garnacho won a penalty in the 10th minute when he checked back inside the area and went down under a challenge from James Tarkowski. Referee Simon Hooper pointed to the penalty spot, with the decision checked by the VAR (watch here).
VAR decision: Penalty stands, scored by Bruno Fernandes.
VAR review: Some might believe this is a modern penalty, with Garnacho realising the challenge is coming from Tarkowski and going down as soon as he feels the contact. Yet unlike some soft penalties this season that should have been overturned (Newcastle's at Wolverhampton Wanderers and Sheffield United at home to Wolves being two examples), Hooper's on-field decision isn't going to be seen as an error as Tarkowski makes contact with Garnacho around the ankle area.
What happened: Garnacho was again at the heart of the action in the 34th minute when he made a driving run into the box, going to ground as Ben Godfrey attempted to make a tackle. Again the referee gave the spot kick (watch here).
VAR decision: Penalty stands, scored by Marcus Rashford.
VAR review: There are perhaps similarities to the level of contact, the difference here being that Garnacho is moving at speed into the area when Godfrey stands on his foot. Another good decision from the referee that was easy to uphold for the VAR, David Coote.
What happened: Manchester United wanted a third spot kick in the 45th minute when the ball hit an arm of Vitalii Mykolenko. Referee Hooper immediately waved away the appeals.
VAR decision: No penalty.
VAR review: Like the Berge situation in the West Ham vs. Burnley game, there is a handball exemption against a player who is using an arm to support his body when going to ground or sliding.
If the defender makes a sweeping motion, or deliberately moves the arm to the ball, then he can still give away a penalty.
In this case, Mykolenko is sliding to block a cutback with both arms in the same position. The VAR was correct to not get involved.
What happened: Ollie Watkins broke into the area in the fifth minute. Tottenham Hotspur defender Micky van de Ven attempted to make a challenge, getting a touch on the ball before making contact with the Aston Villa striker's foot (watch here).
VAR decision: No penalty.
VAR review: VAR protocols indicate that if a defender gets a touch on the ball then a penalty shouldn't be awarded unless the challenge is reckless.
Many will believe that the touch from Van de Ven is too slight, and therefore the nature of the contact on the opponent should take precedence. That said, despite needing treatment Watkins himself didn't appeal for a penalty.
What happened: Aston Villa midfielder John McGinn was sent off in the 65th minute when he kicked out at Destiny Udogie (watch here).
VAR decision: Red card stands.
VAR review: An easy on-field decision for referee Chris Kavanagh, who had a great view of the way McGinn came across and had no interest in trying to play the ball.
The challenge was with force and had to endanger the safety of the Tottenham player.
What happened: Dominic Solanke brought AFC Bournemouth back into the game in the 66th minute. Dango Ouattara's shot was blocked inside the 6-yard box by Jack Robinson, Solanke picked up the loose ball and fired past goalkeeper Ivo Grbic.
VAR decision: Goal disallowed.
VAR review: An easy overturn for the VAR, Michael Salisbury. The ball touched the arm of Solanke as he controlled it following the rebound off Robinson. A player cannot score if the ball touches the hand or arm immediately before he scored, even if accidental.
Some parts of this article include information provided by the Premier League and PGMOL.