Webb, speaking on the Match Officials Mic’d Up show, said that while he accepted there would be a difference of opinion, there were valid reasons for the goal to be ruled out.
“Interfering with an opponent where the offside position player doesn’t play the ball and the officials have to make a judgment whether the actions of that player impact an opponent, are some of the most subjective decisions that we have to make,” said Webb.
“Therefore, it’s no surprise that some people believe this goal should have stood, so I think it’s important that we look at the facts of what actually happened in this situation.
“We know the corner comes in and the ball reaches Van Dijk. As the ball’s coming across the penalty area, the Manchester City players move out, they leave Robertson in that offside position in the heart of the six-yard box.
“When Van Dijk heads the ball forward, that’s the moment when we have to make an offside judgment about Robertson and about what he’s doing there.
“We know he doesn’t touch the ball but what does he do? Well, as the ball moves towards him, three yards out from goal, right in the middle of the six-yard box, he makes that clear action to duck below the ball.
“The ball goes just over his head, and the ball finds the goal in the half of the six-yard box where he is. Then, the officials have to make a judgment – did that clear action impact on Donnarumma, the goalkeeper, and his ability to save the ball? And that’s where the subjectivity comes into play.
“Obviously that’s the conclusion they drew on that. They looked at that position, they looked at that action, so close to the goalkeeper, and they formed that opinion.
“I know that’s not a view held by everybody but I think it’s not unreasonable to understand why they would form that conclusion.
“The player is so close to the goalkeeper, the ball’s coming right towards him and he has to duck to get out of the way of the ball – and they form the conclusion that that impacts Donnarumma’s ability just to dive towards the ball and make that save.
“And then, of course, once they’ve made that on-field decision, the job of the VAR is to look at that and decide, was the outcome of offside clearly and obviously wrong?
“Only Donnarumma truly knows if he was impacted by this and, of course, we have to look at the factual evidence, and when we see that factual evidence of that position of the player ducking below the ball, so close to the goalkeeper, the VAR determines that the outcome of offside is not clearly and obviously wrong, and they stay out of it.”