Sometimes, when I want to remember the way things used to be, I watch footage of Vinnie Jones's tackle on Steve McMahon in the 1988 FA Cup final between Wimbledon and Liverpool.

McMahon's first touch allows the ball to run away from him a little and he has to chase it. Jones senses this and steams in. McMahon gets to it first and nicks it away and Jones flies in, studs up, and takes him out just below the knees.

McMahon gets up. He does not remonstrate with Jones. Nor does he remonstrate with the referee, Brian Hill. Hill is on the scene quickly. He waves the players away and restarts play. He awards Liverpool a free-kick but he does not book Jones, much less send him off.

Jurgen Klopp suffered the biggest defeat of his Liverpool managerial career after 105 games

Manchester City took the lead against the run of play through Sergio Aguero's landmark strike

The turning point in the game hinged on Sadio Mane's sending off but Jon Moss had no choice

You can pine for those days if you want. You can wish, too, that the tackle from behind was still allowed. You can say that football has gone soft. You can say that the game has gone. You can hark back to an era when Marco van Basten was kicked out of a beautiful career and say those were the times when men were men.

But whether you preferred the rules of football the way they used to be or whether you prefer them now, those days have gone and they are not coming back. The rules have changed and players have had to change with them.

That Wimbledon-Liverpool final was nearly 30 years ago. Chopper Harris and Tommy Smith were in their prime 15 years before that. If they played now the way they played then, they would be sent off in every game.

Times change. Rules change. It is not enough to earn redemption now to say that a player was watching the ball when he made a tackle. It is not enough to say he went for the ball. It is not enough to say he is not the kind of player who deliberately hurts an opponent. It is not enough to say he had every right to go for the ball.

Those excuses sound tired. They sound like echoes from another era. And yet they were trotted out one after another yesterday after Liverpool's Sadio Mane lunged for a high, bouncing ball and dealt Manchester City goalkeeper Ederson a sickening blow to the head 37 minutes into their clash at the Etihad Stadium.

It is important to point out that nothing about Mane's foul on Ederson was malicious. He was indeed watching the ball and the collision happened at speed. Mane had also, coincidentally, been Liverpool's best player until that point. He had made John Stones and particularly Nicolas Otamendi look desperately uncomfortable.

Gabriel Jesus headed City into a 2-0 lead before the interval, leaving the Reds an uphill task

Aguero was unselfish in setting up Jesus for his second of the afternoon as City ran riot

One Mane turn and pass to Mohamed Salah after half an hour should have led to a Liverpool equaliser at the Etihad after Sergio Aguero had put City ahead midway through the half.

A couple of minutes before that, Mane had struck fear into City's defence with a mesmerising run that was brought to a crashing end when he was scythed down by Fernandinho.

City were impressive, although how impressive was difficult to judge because their opponents were at a one-man disadvantage for so long.

Kevin De Bruyne, in particular, was a joy to watch and Aguero's unselfish pass to Gabriel Jesus for City's third goal was a sign of a team beginning to buy into Pep Guardiola's ideal of collective beauty.

Leroy Sane came off the substitutes bench to score twice during a very impressive cameo

The game swung firmly in City's favour in the 37th minute after Sadio Mane's red card

Ederson was caught in the cheek by a high boot and referee Jon Moss dismissed Mane

Ederson lay prone on the ground following the 50-50 collision which was a major talking point

City may have won 5-0 in the end but that should not obscure the fact that their defence still looked fragile in the half an hour and more before Mane was sent off. With City trying to play offside, Mane was desperately close to latching on to a through ball from Joel Matip when he smashed into Ederson.

But the facts that Mane is a man to admire and a fine player are not relevant here, either. Once the Liverpool forward raised his foot to head height in pursuit of the ball, he had to make sure he got it because if he got the man instead, then the laws of the modern game say referee Jon Moss had to give a straight red.

Mane did not get the ball. Ederson got there first and Mane kicked him in the head. Inadvertently, yes. But that does not matter. Say the ball had been lower and in midfield, and Mane had lunged for it like that and taken out an opponent at the knee — would it matter then that he had been going for the ball? Of course not. It would still be a straight red.

The Senegalese couldn't believe the decision from Moss to dismiss him with a straight red

Ederson allayed injury fears after medical checks following reckless Mane challenge

The FA's rules say that serious foul play is a sending off offence. One of the definitions of serious foul play is this: 'A tackle or challenge that endangers the safety of an opponent or uses excessive force or brutality must be sanctioned as serious foul play.

'Any player who lunges at an opponent in challenging for the ball from the front, from the side or from behind using one or both legs, with excessive force or endangers the safety of an opponent is guilty of serious foul play.'

So it's a no-brainer. Mane's tackle ticked all the boxes for a red card. It was high, late, reckless and he was out of control. And yet the decision to send him off still created a storm of derision from some ex-professionals who said — yes, you guessed it — the game's gone soft.

Guardiola was delighted with the manner in which his side capitalised on the extra man

Klopp said that Mane was 'very, very upset' with the outcome of his challenge on Ederson

Well, it may have gone soft but it's the way it is now and you have to live with it. You can't try to take it back to the 1970s for a split second when it suits you. Moss got the decision absolutely right although the abuse that was aimed at him afterwards proved yet again what an unenviable job the modern referee has.

Some accused him of ruining the game. I'm sorry but that's garbage. Mane ruined the game by misjudging his attempt to get the ball and kicking Ederson in the head. The referee merely applied the rules.

Save your ire for proper stupidity, such as Fifa pursuing Dele Alli for a jokey gesture to a team-mate. Not for a referee who showed a red card for a challenge that led to a goalkeeper being carried from the pitch on a stretcher.