Despite a successful opening weekend of Rugby World Cup action, a familiar issue has reared its head — in more ways than one — after the first round of matches.

Fans, players and coaches were all left scratching their heads over the seemingly random lottery of what constitutes a red card offence when it comes to head contact, with three seemingly similar incidents leading to three very different outcomes.

Rugby union has increasingly focused on the impacts of head injuries and attempting to mitigate them as much as possible in a full-contact tackle sport.

As such, any contact with the head has been entirely outlawed.

There was no clearer indication of how rugby has clamped down on head contact — whether accidental or otherwise — than in the opening minutes of England’s clash against Argentina.

England flanker Tom Curry made head-on-head contact with Juan Cruz Mallía as the Argentine fullback claimed a high ball.

Tom Curry hits Juan Mallia in the head

Tom Curry was correctly sent off for this collision.(Getty Images: Lionel Hahn)

Curry was shown a yellow card initially, which was upgraded to red by the Foul Play Review Bunker — in use for the first time at this World Cup.

It was, however, England’s third red card in their past four matches, with Owen Farrell and Billy Vunipola both suspended for high shots for this match against Argentina and next week’s match against Japan.

Even within that match though, supporters howled at supposed inconsistencies.

England supporters were then left incensed that Santiago Carreras was only given a yellow card for leaping into George Ford, hitting his shoulder with his hip.

Head coach Steve Borthwick said he would not comment on the disciplinary process regarding Curry, but described the failure to upgrade Carreras’s yellow as “interesting”.

“It looked very similar to an instance a few weeks ago that got upgraded to a red,” he said.

Santiago Carreras stands over George Ford

Santiago Carreras thought he was in trouble after crashing into George Ford.(Getty Images: Dan Mullan)

The similarity of incidents, however, is apparently no indicator on whether they should be adjudicated the same way.

Scotland were left “frustrated” by the lack of consistency on offer from the officials when Jesse Kriel escaped punishment for a head clash with Jack Dempsey in the opening collision of a brutal contest.

“I saw it from two screens away,” Gregor Townsend, Scotland head coach, said.

“It did look like it was a head-on-head collision and I was expecting the TMO to come in and make the referee aware of that.”

Unsurprisingly, outspoken Springbok director of rugby Rassie Erasmus had a different view on the incident.

“We are really comfortable [with the incident],” he said.

“If it isn’t direct head contact — and it wasn’t, it was tackled on the ball and then he moved up after tackling on the ball. I’ve seen a few stills where people just [show] after direct contact to the ball.

“If you took it a millisecond or a second or two back, you’ll see that he clearly tackled on the ball. So we’re very happy with how it was refereed.”

Jesse Kriel puts his hand up to his head

Jesse Kriel escaped punishment for a hit early in a brutal contest with Scotland.(Getty Images: Cameron Spencer)

Townsend said there was no real way of saying whether a red or yellow card in that instance would have had an impact on the game, pointing to England’s stunning 14-man win against Argentina the day prior.

But it’s hard to say it would not have had some role in a bruising contest.

To complete the punishment bingo for head clashes in the opening rounds of the tournament, there were other cases of head clashes experiencing differing levels of punishment.

In the match between Japan and Chile, Martín Sigren committed a head-on-head upright tackle.

His punishment? A yellow card.

In the brilliant clash between Wales and Fiji, Dan Biggar committed an upright tackle on Semi Radradra, with footage appearing to show the Welshman making contact with the former NRL man’s head.

That one went unpunished — far from the only questionable decision that went against the Pacific Islanders in that contest.

Matthew Carley stands

Referees are under the spotlight at the Rugby World Cup.(Getty Images: PA Images/David Davies)

Advocate group Progressive Rugby, which campaigns for more awareness around head injuries in rugby union, posted on X, formerly known as Twitter, that controversy is to be expected.

“It’s of no surprise that there’s controversy at [the Rugby World Cup] around decisions involving a clash of heads,” the group wrote.

“[We] Respectfully ask World Rugby make a designated spokesperson (closely involved in the process) available to studio panel to help fans with clarity/transparency around decisions.”

The process by which referees reach their decisions is relatively straightforward.

Ross Tucker, who posts under Science of Sport on X and works as a sports scientist for World Rugby, explained in a series of posts that “intent” is not part of the decision-making process.

“When a card is given, irrespective of colour & regardless of your level of disagreement with it, please keep in mind that judgements of “intent” and/or “malice” are not fundamental to what match officials look at to reach their decisions,” he wrote, posting a picture of the decision-making flow chart.

World Rugby head contact rules

The World Rugby decision making flow chart for when a head impact takes place.(Supplied: World Rugby)

“Foul play is not only the result of deliberate, intentional or malicious actions. Foul play can exist when they’re absent.”

And not all head contact will result in a red card, or even a yellow.

The laws allow for mitigation, such as if a ball carrier makes a sudden and significant drop in height and there is no time to readjust by the tackler, or another player gets involved in the tackle leading to a rapid change in direction of the ball carrier.

The controversy over red cards and their use is not new.

Wallabies coach Eddie Jones said “the game’s gone out of control” after the second Test between England and Australia in Brisbane last year, when he was coach of England.

“We’ve gone the full hog, where everything is a yellow card, everything’s a red card and there has to be some kind of common sense coming back into the game,” he said.

“I think we’ve gone too far.”

He even suggested, perhaps presciently, that the referee would be “the most influential player” at the Rugby World Cup.

“The team that develops the best cohesion and being adaptable to red or yellow cards and being adaptable to the way referees are refereeing the game will be crucial,” he said.

But as the weekend showed, different decisions are still confusing those involved.

“There are still inconsistencies in seeing these things,” Townsend said.

“We are frustrated by that.”

They aren’t the only ones.