For Waratahs captain Michael Hooper, player safety is paramount. But when it comes to policing tackles above the 'nipple line', he has some concerns.

The 26-year-old loose forward addressed the proposed change to what is deemed a high tackle, and said it's going to be a tough margin to enforce.

"As a forward carrier, you drop your body height to carry into a highly congested zone. So, that's going to make a lot of tackles high because you just can't get any lower," Hooper said. "They're leading with their shoulders and head."

World Rugby is set to introduce a trial law change at under-20 competitions that lowers the acceptable height of a tackle to "below the nipple line" to reduce the risk of head injury.

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The current height for a legal tackle is in line with the shoulders. But, after research revealed that 76 per cent of head injuries occurred in the tackle, World Rugby believes the change could reduce risks, particularly of concussion.

"Everything's experimental, so it'll be interesting to see how that plays out. Anything for player safety is paramount. "

Waratahs coach Daryl Gibson had similar thought to that of Hooper, noting the proposed rule would just add to the confusion around what's high and what isn't.

"I'm certainly supportive of anything that helps safety. I think it's important for the code that we promote laws that certainly assist in that area," Gibson said.

"It's like any new law – it's experimental, it's going to be in the administrating and the implementation – what does that look like? Until we find that out, even now, we're still getting some confusion around what's high and what's not, so it's a bit like the yellow-card rule on knockdowns, we're getting there. It's taken halfway through the comp' to get there, so we'll see."