Tottenham defender Micky van de Ven had rushed over in a desperate attempt to block a shot from Alexander Isak. The Liverpool striker was too quick, firing into the corner to open the scoring at Tottenham Hotspur Stadium.

While Isak came away with a goal, he also faces an extended period on the sidelines after being injured in the process. Was it an inevitable collision between striker and defender? Or was there a case for a red card to Van de Ven?

Rightly or wrongly, defenders are rarely penalised for their challenges after a shot is struck by an attacker. These are tackles which you would expect to be punished if they happened elsewhere on the pitch. The Premier League's Key Match Incidents (KMI) panel voted 3-2 that Manchester City should have been awarded a penalty at Newcastle last month. Fabian Schar had kicked through the boot of Phil Foden after he had taken a shot, but there was no VAR intervention.

As Isak scored there is obviously no case for a penalty. But could the VAR have deemed it a red card for serious foul play? Opinions may be influenced by the injury to Isak but it does not have to be the result of foul play - it can simply be an unfortunate consequence.

It is important to look at how Van de Ven makes the challenge, and also how Isak comes to sustain the injury. As Isak releases the shot, Van de Ven slides in to try to make a block. Crucially, it is Isak's shooting foot that gets injured after he plants it. The foot lands between Van de Ven's legs, and that is how the Sweden striker's injury appears to happen.

Had Van de Ven gone through Isak's standing foot or tackled his opponent directly this would have been a different discussion. But Van de Ven goes to make a block into the space in front of Isak. It was a genuine challenge and should not be seen as a red card.

That does not mean a defender cannot be sent off if they try to stop a shot and clatter into an attacker. We can look at the double leg fracture sustained by Manchester United's Luke Shaw in a Champions League game against PSV Eindhoven in 2015. Shaw had burst into the area to take a shot when Hector Moreno crashed into him, taking his standing foot away in a scissors tackle. It came in the days before VAR, so Moreno did not even concede a penalty let alone get a red card. But it is exactly the kind of blocking tackle which should see a player sent off now.

Van de Ven's challenge, however, appears to be an accidental collision as part of a normal defensive action. Tottenham boss Thomas Frank was not happy with several decisions which went against his side in Saturday's 2-1 home loss. Xavi Simons was sent off after catching Virgil van Dijk on the back of the calf as he closed down the Liverpool defender. Referee John Brooks had only shown a yellow card, but was sent to the pitchside monitor by the VAR Stuart Attwell. Frank said "the game is gone if that's a red card". Yet the consensus among former players was it was the right decision.

On Match of the Day, Joe Hart said: "That is such a dangerous tackle, he's caught him on the back of the Achilles, it's absolutely a red card." Referees' chief Howard Webb last season made it clear this kind of challenge should lead to a VAR review. His comments came after Leicester City's Wilfred Ndidi was not sent off after raking his studs down the calf of Chelsea's Cole Palmer in an incident which was similar to Simons on Van Dijk. Webb said of Ndidi's foul: "We've looked at this collectively, among the officials, talked about this, and we would prefer this to be dealt with with a red card. We have to protect player safety."

But what about a possible red card for Alejandro Garnacho earlier in the day? The Chelsea forward only received a caution for his foul on Newcastle's Jacob Ramsey. The decision of referee Andy Madley was supported by the VAR Peter Bankes.

There are some important differences to consider. The ball was in playing distance when Garnacho started the challenge. While he did then lead into Ramsey with his studs there was no force or intensity - and only a small amount of contact. If a player is stepping into a tackle and mistimes it slightly a caution is seen as an acceptable disciplinary outcome, even if initial contact is above the boot.

Challenges from behind, as with Simons, where there is no possibility of getting to the ball are far more likely to result in a red card. If Frank was annoyed about the Simons red, he was even more angry about Liverpool's second goal. Jeremie Frimpong's cross took a slight deflection, and Huge Ekitike rose above Cristian Romero to head home.

"There is a massive mistake by John [Brooks] on the pitch. Two hands on the back by Ekitike," Frank said. "Luckily we have VAR so they will bail you out when you need it, which they didn't." Ekitike's hands were on Romero, but there did not appear to be any force applied to foul the defender. It looked like a strong, powerful header.

Earlier this season Manchester United scored at Fulham when Leny Yoro had two hands on the back of Calvin Bassey. The goal stood after a VAR check. The KMI panel voted 3-2 that it should have been ruled out on the field, but 4-1 that it had not reached the threshold for the VAR to intervene. Yoro had pushed slightly forward on the back of Bassey, but there was no such action from Ekitike on Romero. It is very unlikely the panel would see the Ekitike goal as an error by either the referee or the VAR. Former Newcastle goalkeeper Shay Given agreed on Match of the Day: "I think John Brooks has got it right."