ADELAIDE veteran Reilly O'Brien says he is still adjusting to the new ruck rules for 2026, conceding there is some uncertainty among players and umpires alike around what manoeuvres are still allowed at centre ball-ups.

Among the seven rule changes for the 2026 season announced by the AFL last year, competing rucks will now be unable to cross the centre line before engaging with their opposition ruck.

The AFL hopes the change will see jumping rucks return to the game, with the League's analysis finding just 21 per cent of centre bounce ruck contests in 2025 had at least one jumping ruck, down from 63 per cent two years earlier.

O'Brien says the change should suit athletic, jumping rucks like Tom De Koning and Luke Jackson, and that stronger, bigger players like himself are now searching for ways to counteract the move.

In match simulation with umpires at West Lakes on Wednesday, O'Brien conceded several free kicks as he 'tested the limits' of what is and isn't allowed under the new rules, and said more clarity is needed before the start of the new season.

"It will suit the jumpers. I think that's what it's designed to do, to help guys like Tom De Koning, Luke Jackson, Bailey Williams - those guys who are pure jumpers at the ball," he said.

"It gives them a chance to show their strengths in there and not get wrestled out of it. So against those guys it will certainly be a challenge.

"Against the big bruisers like Tristan Xerri or Darcy Cameron, it might be more of an advantage for a guy like me.

"I'm still trying to work it out, and I think (the umpires) are too, to be honest. It's a bit grey so far.

"They're adjudicating on stepping over the line before you jump -  that's the main cue they're looking for. And there's a few other things we're working through as well, like whether you're allowed to collide with the opposition ruckman before hitting the ball.

"It's a bit grey for us and for them, so I was trying to test the limits of it today and I gave away about four frees. I'll need to go and watch the vision because I'm not exactly sure what they were for.

"We'll work it out; there's a bit of clarification from the AFL to come and then the umpires and players."

O'Brien said testing himself against former Sydney ruck Lachlan McAndrew, who is eight centimetres taller than him, has given him the perfect chance to try new techniques ahead of battles with rucks who can jump higher than he can.

"You're not going to be able to outreach certain guys with a pure jump, so it's a matter of trying to find out what you can do in there as an opposing ruckman," he said.

"Do the AFL want to make it a pure reaching and jumping contest, or (is) there ... scope for some ruck craft in there, to be able to jump a bit early, collide and bounce off and use your back hand?

"It's a matter of what is allowed there from an umpiring point of view."

This week, AFL.com.au spoke with multiple coaches and officials as clubs work through strategies for all of the new rule changes heading into this season. 

One coach supported O'Brien's view that there is still some grey area around first point of contact at centre ball-ups, and that the upcoming match simulations would be pivotal chances for rucks to adjust.

"You can take the opposition ruckman's space as long as you don't cross the line so you can still jump early. But as long as it doesn't turn into just 'Who is the highest jumper?'," one coach said.

While ruck work at centre ball-ups will change, there will still be an opportunity for more physical ruck work at around-the-ground stoppages and boundary throw-ins.

Umpires will now also be able to restart play without a nominated ruck being present, which some coaches believe could see bigger-bodied midfielders take on second-ruck duties.