In the latest edition of Ref Watch, former Premier League referee Dermot Gallagher highlights an important lesson for assistant referees after Paul Pogba's contentious equaliser at West Ham.
Dermot joined Rob Wotton on Sky Sports News to review the weekend's big decisions...
West Ham 1-3 Man Utd
INCIDENT: Manchester United goalkeeper Dean Henderson's clearance along the touchline went out of play in the build-up to Paul Pogba's equaliser at the London Stadium. It was missed by the on-field officiating team and VAR was unable to overturn due to insufficient evidence.
VERDICT: "There's a couple of issues here. The guy that had the best view didn't use it. The assistants prioritise offsides and the ball out of play. In this situation the ball was so far down the wing when Henderson kicked it that offside is immaterial at that point, the key issue is where is the ball going to go.
"The assistant is looking straight across the field at the offside and doesn't see the flight of the ball, so it didn't get picked up on the field. When it went to VAR, there was no conclusive evidence that the ball had gone out.
"It looks out, and subsequently we have seen it did go out, but the calibration is horizontal - there is not lateral line - so they couldn't calibrate from corner flag to corner flag to see the ball had gone out. It's just one of those things that got missed.
"David Moyes' reaction wouldn't be a cue for the referees, who are focusing on matters on the pitch. But rather than priority being offside and then move down the chain, be adaptable. The primary concern was not offside, it was whether that ball could go out of play, and that's the learning point from that situation."
West Brom 1-5 Crystal Palace
INCIDENT: Referee Paul Tierney overturns his original decision to award Matheus Pereira a yellow card with a straight red card after consulting the pitchside monitor and spotting the West Brom midfielder had lashed out and thrusted his legs into Crystal Palace defender Patrick van Aanholt.
VERDICT: "When I watched the game, I didn't know what the officials were checking. But when I saw the incident, and the referee go to the screen, I knew it was going to be a red card.
"People ask whether it was enough of a kick out, but argument to that would be why does he need to put his boot there? What's the point of putting his boot there? He's doing it for some reason, and the reason isn't balance or to get up off the floor. It is to push his boot towards an opponent, and on that basis, it is a red card. It's inevitable."
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Liverpool 4-0 Wolves
INCIDENT: Referee Craig Pawson changes his decision to award Wolves a penalty after being instructed to consult the pitchside monitor and ruling Sadio Mane had in fact pulled out of a challenge on Conor Coady before the Wolves captain went to ground in the area.
VERDICT: "Thumbs up for VAR, absolutely. When you see the replay, Mane clearly pulls his boot away before Coady goes to ground. The referee is alerted to go to the screen, he sees what we have all seen, and he quite rightly overturns it.
"It's definitely not a penalty, but without VAR it would have been given. This is a real plus for VAR because this is what we talk about."
Chelsea 3-1 Leeds
INCIDENT: Ben Chilwell challenges Leeds winger Ian Poveda in the box and makes contact with man and not ball. Poveda stays on his feet but the phase comes to nothing as Edouard Mendy saves the winger's tame effort. VAR did not intervene, and Kevin Friend's decision not to punish the challenge stood.
VERDICT: "If Poveda goes down, the referee has a different decision to make, there is no doubt about that. I have said in the past that referees need to be aware that a foul can be committed even if a player stays on their feet.
"What I would say is that VAR was wise to stay out of this because it's not there to decide whether the referee has got something wrong, it's there to make a judgement whether a player, manager, coach or spectator in unison would say that something is definitely wrong, a clear and obvious error.
"I would say on that basis, this decision needed to be left to the referee on the field. It's a very different decision when a player stops on his feet, and this is why players say they go to ground. We have talked about it for years and year.
"We never know, the referee may have made the same decision had Poveda gone down, but on the evidence of what I saw on Saturday and the protocol I have read through, the VAR had no right to intervene."