Sonny Bill Williams' indefensible offload changed rugby union and Israel Folau's vertical leap has the potential to do the same, according to new NSW Waratahs assistant coach Daryl Gibson.

Former All Black Gibson, who helped mould the Crusaders' potent backline when Williams made his Super Rugby debut, watched Folau train for the first time with NSW on Thursday.

It was a low-key hit-out, with Folau laying a couple of slick passes and making a handful of line breaks during drills, but Gibson was already thinking big about the impact a bulked-up Folau can have on the 15-man game.

"Sonny brought to union some skills he had from league and he's changed our game," Gibson said.

"Israel, particularly with his aerial ability, could potentially do the same.

"It's not a skill we're particular adept at. He spent two years catching and kicking (in the AFL) and we'd be foolish not to utilise that skill."

Gibson, part of the Crusaders' foundation squad in 1996 and involved in union ever since, said he'd never seen anything like Folau's ability to leap and snaffle the high ball.

"And what I haven't seen in union a lot is the ability to catch the ball above your head, and that's a skill he's going to bring to our game," Gibson said.

"Absolutely (it could change the game) and what it will change is teams' ability to defend us.

"If the backfield is worried about his aerial game, then it obviously opens up opportunities elsewhere on the field.

"We're going to have to exploit that."

Folau spoke of his desire to take on the All Blacks on Tuesday, and Gibson revealed the 23-year-old's switch to union had already created waves in his rugby-mad homeland.

"I got a number of texts from people back in New Zealand who were excited to see him go," Gibson said.

"A few (Super Rugby) coaches and obviously players (sent messages). It's neat that they're aware we've signed someone of his calibre."

Folau, who coach Michael Cheika says will play in the back three, will initially be shielded from contact work while he learns the intricacies of the ruck.

The code-hopper's other major challenge will be to re-design his physique after shedding seven kilograms to prepare for the endurance required in AFL.

But Cheika said Folau will do a lot of running without the ball for the 'Tahs and his body transformation won't be overly severe.

"Maybe somewhere in the middle (of his playing weights in AFL and NRL). I can't be sure, there's no exact science to this," Cheika said.

"I don't know if it's about upper chest or lower body. Most players know the weight they feel comfortable at. You got to go with your gut feel.

"It (Folau's preparation for Super Rugby) is not really about that. It's about footy."

- AAP