Tackling is at the heart of Australian football, as intrinsic as the crowd crying “baaall” at the umpire whenever a player is grabbed. A well-applied tackle at a critical moment can turn a game. It can change momentum, lift a team and thrill a crowd. But when a tackle goes wrong, the result can be devastating, leaving a player with serious head or neck injuries.

In all collision football sports, the tackle is as potentially dangerous as it is central to the way the game is played. And the 360-degree nature of Australian rules means that in the AFL, the tackle carries an additional risk.

All sports have been grappling with the consequences of concussions, sub-concussive episodes and the dangers of repeated head trauma. Dozens of players across codes have been forced to retire because of concussions, and dozens more have reported serious health effects later in life, some of them launching court action against the sport.

With this in mind the AFL, and other codes such as the NRL, have cracked down on avoidable actions that lead to head trauma.

In AFL, players now know that if they choose to crash into an opponent and bump them in the head, they risk being suspended. This year, they are being forced into another adjustment: if they tackle, they have a duty to ensure their opponent’s head doesn’t crash into the ground. Eliminating the “dangerous” tackle is the new frontier in the AFL’s determination to make football safer.

There have been 21 suspensions for dangerous tackles so far this season, and many more have come before the AFL Tribunal.

The rules governing what you can and can’t do in a tackle are changing before our eyes; at least, the threshhold of what is permissible has been raised. Fans are struggling to wrap their heads around the change. So, what makes a dangerous tackle? And what can a player do in tackling an opponent, either to win a free kick for holding the ball or to dispossess them and force a turnover?

Why the crackdown? And why now?

The AFL is unapologetic about its mission to eliminate behaviour that results in serious head injuries while maintaining what purists call “the fabric of the game”; that is, the desperate tackles and tough collisions that make for a thrilling spectacle.

“We continue to make changes that ensure the AFL’s commitment to protect the head of players is reinforced by the AFL tribunal,” then AFL acting head of football Andrew Dillon said early this year.

With both arms pinned, the tackled player had no way to protect himself from impact with the ground.

In the modern game, players who were tackled had become so adept at getting an arm free to dispose of the ball that tacklers were encouraged to pin both the opponent’s arms and bring the player to ground. The consequence of this was that, with both arms pinned, the tackled player had no way to protect himself from impact with the ground. So, players’ heads hit the turf, leading to concussions.

The AFL did not change the tribunal rules to increase penalties for tacklers – they didn’t need to, the rules were already there. They instead started grading more tackles as “dangerous”.

More free kicks are now being paid for dangerous tackles, and more players are being cited by the match review officer. More players have been suspended, and for longer periods.

What makes a tackle dangerous? What can’t you do?

For a long time, “spear tackles” have been outlawed for being absurdly dangerous. A spear tackle is when you lift a player off the ground and almost flip up their legs, so you drive the player head first to ground. Everyone knows you can’t do that. So, no change there; the spear tackle is almost extinct.

“Sling tackles” have gradually been outlawed in recent years. That’s when a tackler has a player off-balance and brings them to ground, with momentum swinging the player, often across the tackler’s body, so the player slams into the ground.

Tacklers will now be punished if an injury caused by a tackle was avoidable.

So, what is an avoidable tackle?

It is in large part about technique. There are different ways to tackle and if you choose a method that causes injury, you will be punished.

If, for example, you have both of an opponent’s arms pinned and you bring him to ground, you have a duty of care not to drive him into the turf so that his head slams into it.

An example of this is when Hawthorn’s Will Day tackled Brad Close from Geelong earlier this year. Close had no chance to protect himself. Day was also punished because his second act was to drive Close to ground. Day was suspended for two matches. He would have been suspended for longer but for the fact that Close got straight up and was not hurt or concussed. Watch it here:

Nathan Broad’s tackle on Patrick Parnell was similar: both arms pinned, slammed to ground. Parnell was concussed and subbed straight out of the game. Broad got four matches; it would have been longer save for a guilty plea. The AFL, in punishing him, explained that players have a duty of care when an opponent player is vulnerable. In that instance, the tackler is responsible for trying to avoid injuring them.

The AFL Tribunal this year is issuing an explanation with every decision to give guidance for players, coaches and fans.“Broad had Parnell wrapped up. Parnell was vulnerable. He had no realistic prospect of protecting himself, and his head was slung to the ground with considerable force. He has suffered a concussion and there was the potential for additional injuries,” the tribunal statement read.

More critical was this additional point: “We have said previously and we repeat tonight players must do all that they reasonably can not to cause avoidable head injuries to their fellow players. Every player is now taken to be aware of the damaging and sometimes long-term consequences of concussion.”

What about Carlton’s Adam Cerra? Didn’t he, too, slam his opponent, Sydney’s Tom Hickey, to the ground? Have a look at this video clip:

This tackle does look similar to the Broad one, but other TV angles showed Hickey had one arm free holding the ball and could have better protected himself.

“A reasonable player in Cerra’s circumstances would know that Hickey could use one or both of the arms to break his fall,” the tribunal said. Cerra challenged his one-match suspension at the tribunal and was cleared.

Then there is the James Sicily tackle, which polarised opinions and resulted in the Hawthorn captain being suspended for three matches, which was upheld by the AFL Appeals Board. You can check it out here:

Was Sicily responsible for Brisbane Lions star Hugh McCluggage being knocked out?Sicily had hold of McCluggage and swung him over his body just as his Hawthorn teammate Tyler Brockman came running past and also knocked McCluggage. The tackle ended with McCluggage’s head slamming into the ground.

The footage that showed Brockman accidentally knocking McCluggage in the pack made it difficult to work out which action was responsible for the Lion’s injury.

The tribunal found, from viewing multiple angles, that while Brockman’s contact was incidental it didn’t change the fact Sicily was pulling down on McCluggage’s left arm as he rotated him in the tackle. By pulling down on the arm to bring McCluggage to ground he caused the Lions player’s head to hit the ground.

“We do not accept that Brockman’s involvement caused an otherwise safe tackle to be dangerous,” the tribunal said. “He [Sicily] could have released the left arm. Had he done so McCluggage would not have been rotated across his body and into the ground with such force. Accordingly, we find this was a dangerous tackle.”

The AFL does want him to let one arm go so the Brisbane player can protect himself as he hits the ground.

Does this mean Sicily is supposed to let McCluggage get away? Not entirely, but the AFL does want him to let one arm go so the Brisbane Lions player can protect himself as he hits the ground.

St Kilda’s Dan Butler has admitted players are struggling to adjust to the new expectations as they make the split-second decision to tackle. Butler’s run-down tackle of Nick Blakey at high speed went to the tribunal, but he was cleared. Watch it here:

The tribunal said Butler had made best endeavours to avoid injuring the player. Butler turned Blakey slightly in the tackle so as not to go into his back, and at the last moment let Blakey’s arm go. It was not obvious live, but replays showed it.

“The question is not whether he released [an arm] in time for it to be effective ... the question is whether he did so as early as he reasonably could. We find that he did,” tribunal chairman Jeff Gleeson said.

“Releasing an arm or not pinning an arm will not always be enough to avoid breaching the duty of care but here, where the fact that the tackled player would be brought to ground was inevitable and unavoidable, it was an important consideration.”

What makes a perfect tackle?

The AFL recently addressed this question. Acting footy head Laura Kane sent a memo to clubs applauding a change in behaviour from players and showed examples of how players had tackled well even when bringing players to ground with arms pinned. In the clip below, Collingwood’s Beau McCreery releases an arm and eases, instead of increases, the force bringing Richmond’s Daniel Rioli to ground.

Now watch as Melbourne’s James Jordon could have swung with his momentum and slammed Liam Shiels into the ground but instead slows momentum and drops at his knees.

Here, St Kilda’s Brad Crouch rides with the player and gets under the tackle to lessen the impact.

While these are all split-second moments, as Geelong captain Patrick Dangerfield said on radio this week, he has already changed his behaviour. And Butler, who did release his opponent’s arm at the critical moment, has said players are acutely aware of their responsibilities. “All of us players are aware of the ramifications of a dangerous tackle,” he said.

“I think over the last couple of years, there has been an evolution of tackling. It has gone from probably initially trying to hurt them [an opponent] and leave them on the ground to, obviously, rolling more and being a lot more careful. It’s a difficult one. We are still trying to adapt to it.”

Fremantle coach Justin Longmuir has started teaching players not to use a “second action” to drive players into the ground, and speculated that the next phase might be to instruct players not to bring opponents to ground at all, but to merely hold them up.

The AFL’s message, it seems, is sinking in.

“It’s almost at that point, isn’t it,” said Gold Coast coach Stuart Dew, “that if you choose to take a player to ground, if they hit their head, you’re putting yourself at risk?”

Note: Tribunal Chairman Jeff Gleeson KC is reporter Michael Gleeson’s brother.