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: Were Manchester United hard done by with the penalty that resulted in their defeat at West Ham United? Should Arsenal have been given a spot kick against Liverpool? And was Tottenham's Micky van de Ven lucky not to be sent off?
West Ham 2-1 Man United
Possible penalty: De Ligt challenge on Ings
What happened: A cross was played into the area in the 87th minute, with the ball eventually dropping between Matthijs de Ligt and Danny Ings. Both players moved toward it, with the West Ham striker going down holding his shin. Referee David Coote didn't see any foul, so play continued, but it was looked at by the VAR, Michael Oliver.
VAR decision: Penalty, scored by Jarrod Bowen.
VAR review: Whether it was right or wrong comes down to how VAR is applied in the Premier League and what we've come to expect from the video assistant.
In European competition, where pretty much any unexpected lower-body contact appears to result in a penalty, it would come as no shock to see the VAR get involved. In the Premier League, not so much.
There are some grounds here for a foul, because while both players do go into the challenge in a similar way, there is slightly more force from De Ligt. But that doesn't mean there's enough in it for the VAR to get involved. It's more a collision between two players, from which Ings comes off worse.
(Though the ball touched the hand of Ings as it bounced up, this would be considered accidental and not a handball offence.)
The Premier League has been determined to get the term "referee's call" into the lexicon this season, and this would be a perfect example. If Coote gave the penalty, you could see a reason. But it doesn't reach the clear and obvious threshold in English football to send the referee to the monitor.
Bowen's penalty led to a 2-1 defeat for Man United, with Erik ten Hag sacked on Monday morning as a result. It was the second time in a month that the beleaguered boss had suffered from a refereeing error, with Bruno Fernandes wrongly sent off in the 3-0 home loss to Tottenham Hotspur. However, while United did win an appeal against Fernandes' red card, they were already losing and being outplayed when it happened and the VAR failed to intervene. Ten Hag therefore said he chooses to "deny" and "ignore" the Spurs defeat, but he wasn't given the chance to do the same after this VAR error.
PGMOL has been talking up how much faster VAR reviews have got this season, down from an average of 70 seconds per game to 25 seconds. But this took 2½ minutes from the foul to Coote pointing to the penalty spot (and another 2½ minutes until Bowen struck the ball.)
There's a secondary question about the use of the monitor. Why is it there, if we always see the referee change his decision?
The answer is simple, though the waters are muddied by protocol. The screen is supposed to be a safety net on subjective decisions, to give the referee the chance to spot an error by the VAR. That's the idea, but it doesn't really work.
Last season, there were five incorrect VAR interventions where the referee went to the screen and still changed his decision. Refs go to the monitor knowing they are being told they have made a clear and obvious error, and not just to have a second look. The limitations of this VAR process condition referees to think they have screwed up, so the "fail-safe" is in itself flawed.
We'd all like referees to have more conviction and stick by their own call a few times, but it seldom happens. Two referees rejected an overturn last season, yet only one was deemed correct -- when Oliver turned down a review to rule out an Arsenal goal against Everton for handball.
Verdict: Incorrect VAR intervention. Oliver had one recorded error as the VAR last season, when he failed to award a penalty to Brentford at Nottingham Forest, and this will go down as a mistake.
Arsenal 2-2 Liverpool
Possible red card: Van Dijk challenge on Havertz
What happened: The game was only six minutes old when Virgil van Dijk and Kai Havertz tussled off the ball, with the Arsenal player going to ground. Referee Anthony Taylor had words with the two players but took no action.
VAR decision: No red card.
VAR review: Long gone are the days where a little kick is seen as a red card, as it was when England midfielder David Beckham was sent off against Argentina at the World Cup in 1998.
Today, referees look for an act which has a level of brutality to it. While Van Dijk should probably have been booked for throwing his boot back towards Havertz, this would be seen as petulant rather than violent conduct.
Verdict: No violent conduct so correct not to intervene.
Possible penalty: Konaté challenge on Martinelli
What happened: Arsenal were on the attack in the 31st minute when Gabriel Martinelli tried to break past Trent Alexander-Arnold and Ibrahima Konaté. The Arsenal forward went to ground, but referee Taylor waved away the penalty claims.
VAR decision: No penalty.
VAR review: It looked a clumsy situation, as two Liverpool players challenged Martinelli at the same time.
However, Konate got contact on the ball first, knocking it away with his leg, just below his knee. There's then natural contact between the two players after the ball has been played. There's no foul contact by Alexander-Arnold.
Had Konaté gone through Martinelli to play the ball, that would have been grounds for a VAR intervention. However, much like the overturned penalty for Liverpool against Chelsea last weekend, the defending player played the ball first and didn't make the challenge in a reckless way.
Verdict: Correct decision not to award a penalty.
Crystal Palace 1-0 Tottenham
Possible red card: Van de Ven challenge on Sarr
What happened: A long ball was played over the top by Tyrick Mitchell in the 64th minute which Jean-Philippe Mateta flicked on to find the run of Ismaïla Sarr. The Crystal Palace forward looked to have a run on goal when he was fouled by Micky van de Ven. Referee Darren Bond produced a yellow card, and the VAR checked for a possible red.
VAR decision: No red card.
VAR review: Last week we discussed in detail the various factors a referee takes into account when deciding if the boxes have been ticked to give a red card for denying an obvious goal-scoring opportunity (DOGSO). That was around the dismissal of Arsenal's William Saliba at AFC Bournemouth, so what's the difference in this case?
There's no chance of a covering defender getting over, while goalkeeper Guglielmo Vicario is backtracking so not a consideration. Sarr is also much closer to goal than Evanilson when he's brought down.
The yellow card in this instance is an acceptable outcome due to the general direction of play, as Van de Ven and Sarr are running on a diagonal away from goal to get to the ball. For the Saliba red card, Evanilson had a direct run to goal through the centre.
This might seem to be a trivial differences, but it's crucial in the assessment and deciding if the clear and obvious threshold has been reached.
Verdict: The VAR wouldn't have stepped in to cancel a red card had Bond made than decision but, unlike with Saliba, this falls just below a VAR intervention on DOGSO. Van de Ven was definitely fortunate, however.
Chelsea 2-1 Newcastle
Possible penalty overturn: Burn challenge on Nkunku
What happened: Referee Simon Hooper awarded a penalty to Chelsea in the 90th minute when Christopher Nkunku went to ground when he appeared to be pulled back by Dan Burn. The VAR, Jarred Gillett, checked the decision.
VAR decision: Penalty cancelled.
VAR review: Nkunku went down very easily, and while there was some contact on his shoulder by Burn it appeared very slight and not enough to make the Chelsea striker go to down as he did.
Last season, Chelsea were wrongly awarded a penalty against Burnley when Lorenz Assignon was judged to have pulled down Mykhailo Mudryk. There was minimal contact and the VAR should have intervened, as he did in this case.
Though the penalty was cancelled, Sean Longstaff's booking for dissent isn't removed, as it's considered an offence of a player's behaviour, rather than directly related to the award of the spot kick.
Verdict: A good intervention, and the kind of penalty VAR should be overturning.
Aston Villa 1-1 Bournemouth
Possible ball out of play: McGinn goal
What happened: Aston Villa took the lead in the 27th minute through John McGinn. However, AFC Bournemouth players had appealed for the ball being out of play in the buildup when Ollie Watkins had attempted to keep it in. It was checked by Matt Donohue, who was acting as VAR for the first time.
VAR decision: Goal disallowed.
VAR review: Arsenal fans will be triggered by the goal scored against them by Newcastle United almost a year ago to the day. In that match at St James' Park, there was uncertainty about Joe Willock keeping the ball in play in the buildup to Anthony Gordon scoring the only goal of the game.
So, why was the VAR in this game able to intervene and disallow the goal, yet wasn't in Newcastle-Arsenal? It all comes down to the position of the play and the available camera angle.
Willock was close to the corner flag, an area not covered by the goal-line camera as, understandably, the primary focus is the goal itself. So the VAR, Andy Madley, had to use a camera that wasn't directly in line, and due to the curvature of the ball it was difficult to be certain the whole of it was over the line.
Watkins was within the goal-line camera, so the VAR has the best possible view. It was very close, but "daylight" looks to be present between the ball and the line.
A more direct comparison comes from Manchester United vs. Brighton & Hove Albion last September. Rasmus Højlund thought he had equalised, but there was a check for the ball being out of play before it was cut back by Marcus Rashford.
Just like Watkins, Rashford was within the goal-line camera and the VAR was able to be certain that the ball was out.
Verdict: It was certainly a close call, but the evidence is there that the whole of the ball was over the line ... just.
Possible penalty: Cash challenge on Semenyo
What happened: Bournemouth were on the attack in the 80th minute when Antoine Semenyo went to ground when trying to go past Matty Cash. Referee Chris Kavanagh blew his whistle, but to book Semenyo for a dive.
VAR decision: No penalty.
VAR review: The VAR is looking at both the actions of the attacker, and any contact from the defending player.
While Cash slides in to make a challenge, Semenyo is already going to ground before there's any contact between the two players.
If this had been awarded as a penalty, the VAR wouldn't have intervened due to the contact from the defender (remember the spot kick Newcastle United's Anthony Gordon won against Manchester City), but at the same time the way the attacker goes down means it won't be seen as a clear and obvious error not to give and penalty.
And this is where VAR protocol gets very confusing for fans. You can argue it's not a penalty, but also not truly a dive either. So, is it a clear and obvious error to book Semenyo? And if so, does that mean the overall decision should be reviewed? But VAR cannot get involved in yellow cards, so will only send the referee to the monitor if a penalty has been missed, and for no other reason.
Verdict: Not enough for a VAR penalty.
Possible penalty: Handball by Bailey
What happened: Bournemouth won a corner in the 84th minute. As it dropped over the head of Leon Bailey it hit the Aston Villa player's arm. David Brooks, who was behind Bailey waiting for the ball, appealed for a penalty.
VAR decision: No penalty.
VAR review: Had this incident happened last season, there's a strong chance it would have been a VAR penalty. But this season, the arm really does have to be fully extended. The only handball penalty was given against Cash at Fulham last weekend when his arm was pointing out from his body.
Both of Bailey's arms are in a similar position as he spins to follow the dropping ball, and the argument is this is natural movement and not a deliberate act.
We saw two similar situations not result in a handball penalty earlier this season in a game between Nottingham Forest and Wolverhampton Wanderers, including when the ball dropped the arm of Jørgen Strand Larsen as Chris Wood waited to collect the ball.
Verdict: Consistent with other handball decisions this season.
Brentford 4-3 Ipswich
Possible penalty: Position of foul by Harrison Clarke on Lewis-Potter
What happened: Brentford were on the attack in the 49th minute when Ipswich Town's Harrison Clarke brought down Keane Lewis-Potter on the edge of the area. Referee Lewis Smith blew for a free kick, but the VAR, Peter Bankes, had to consider if the offence had continued into the area.
VAR decision: Penalty, scored by Bryan Mbeumo.
VAR review: If holding starts outside the area and continues into the box, then a penalty should be awarded. This is different to a foul tackle, when the point of contact on the opponent's body is used to determine where the offence took place; such a foul can take place outside the box and momentum take both players into it, but that won't be a penalty.
As the position of a foul is considered a factual decision, rather than subjective, it's made solely by the VAR without the referee needing to visit the pitchside monitor.
Verdict: A decision the referee will be disappointed to get wrong, as it was very clear that the holding continued into the box. An obvious VAR overturn.
Some factual parts of this article include information provided by the Premier League and PGMOL.