The nipple line has been scrapped — but rugby's desperate bid to beat concussion could see the game turned upside down if drastic new proposals are successful.
World Rugby is considering new rules which include banning upright tackles and suspending concussed players, the Sydney Telegraph has reported.
This follows research which shows tacklers have the highest concussion risk, particularly when upright.
The proposals - rule changes cannot be introduced before next year's World Cup in Japan - indicate just how fearful and concerned World Rugby is about the head injury situation.
They would change the game forever, and new techniques might prove almost impossible for established players to adopt.
It could have flow-on effects - great offloaders like the tall Sonny Bill Williams might have a field day if tacklers could not confront them high.
The under-20s World Cup trial, requiring tacklers to make contact below the nipple line, was a failure because referees struggled to locate the imaginary line and make decisions on the move.
Now upright tackles may be banned to reduce head-to-head contact. A concussed tackler who was at fault would also be suspended.
The Daily Telegraph report said the move would have ramifications for contact sport around the world, with the NRL league bosses among those keeping an eye on the situation.
World Rugby's chief medical officer Martin Raftery — a former Cronulla Sharks first grade league player — said traditional rugby attitudes must change to drastically reduce concussion, the Telegraph reported.
"The tackle is the phase of the game with the most concussive injuries, and then within the tackles it is the tackler, not the ball carrier, who is most at risk," Raftery said.
"So what we're trying to do through a number of different processes is to bring the tackle height down, to protect more the tackler than the ball carrier.
"Yes we've got to protect the ball carrier as well, but the focus is on the tackler."
There would need to be clear details on what determines if a player is upright, while referees face a potential nightmare making instant decisions around player body angles.
Raftery said a new high tackle warning system would penalise upright tacklers who made contact with ball carriers.
"It doesn't matter whether the ball carrier is injured or the tackler is injured. If the tackler is upright, when there's clear and obvious contact, can receive an extra penalty."
World Rugby studied 611 cases which included 464 concussions in tackles, with the tackler suffering 335 of those.
Raftery said World Rugby was trying to rely heavily on evidence, rather than make rash decisions.
"It seems quite logical; lower the tackle, you're going to reduce the number of head injuries," he said.
"It's not rocket science. If it sounds sensible and is backed by research I think we should be doing it."